SqlHelper.cs通用类之C#连接SqlServer

using System;
using System.Data;
using System.Xml;
using System.Data.SqlClient;
using System.Collections;
using System.Configuration;

namespace GZD.SqlHelp
{
    /// <summary>
    /// 连接、打开和关闭数据库类
    /// </summary>
    public class ConnectionManager
    {
        //不允许实例化
        private ConnectionManager() { }

        /// <summary>
        /// 返回一个数据库连接
        /// </summary>
        /// <returns></returns>
        public static SqlConnection GetSqlConnection()
        {
            SqlConnection conn = null;
            try
            {
                if (null == conn)
                {
                    conn = new SqlConnection(SqlHelper.DBString);
                    OpenSqlConnection(conn);
                }
                return conn;
            }
            catch (Exception ex)
            {

                throw ex;
            }
        }

        /// <summary>
        /// 打开一个数据库连接
        /// </summary>
        /// <param name="conn"></param>
        public static void OpenSqlConnection(SqlConnection conn)
        {
            try
            {
                if (null != conn && conn.State == ConnectionState.Closed)
                {
                    conn.Open();
                }

            }
            catch (Exception ex)
            {

                throw ex;
            }
        }

        /// <summary>
        /// 关闭一个已打开的数据库连接
        /// </summary>
        /// <param name="conn"></param>
        public static void CloseSqlConnection(SqlConnection conn)
        {
            try
            {
                if (null != conn && conn.State == ConnectionState.Open)
                {
                    conn.Close();
                }

            }
            catch (Exception ex)
            {

                throw ex;
            }
        }
    }

    public class SqlHelper
    {
        //public static readonly string DBString = ConfigurationManager.ConnectionStrings["SqlConnectionString"].ToString();
        //public static string DBString = ConfigurationManager.ConnectionStrings["SqlConnectionString"].ToString();
        public static string DBString = ConfigurationManager.ConnectionStrings["SqlConnectionString"].ConnectionString;

        #region private utility methods & constructors

        //Since this class provides only static methods, make the default constructor private to prevent
        //instances from being created with "new SqlHelper()".
        private SqlHelper() { }

 

        /**/
        /// <summary>
        /// 这个方法用来将命令对象和一组参数对象联系起来
        ///
        /// This method will assign a value of DbNull to any parameter with a direction of
        /// InputOutput and a value of null.  给输出类型参数对象赋空值
        ///
        /// This behavior will prevent default values from being used, but
        /// this will be the less common case than an intended pure output parameter (derived as InputOutput)
        /// where the user provided no input value.
        /// </summary>
        /// <param name="command">The command to which the parameters will be added</param>
        /// <param name="commandParameters">an array of SqlParameters tho be added to command</param>
        private static void AttachParameters(SqlCommand command, SqlParameter[] commandParameters)
        {
            foreach (SqlParameter p in commandParameters)
            {
                //check for derived output value with no value assigned
                if ((p.Direction == ParameterDirection.InputOutput) && (p.Value == null))
                {
                    p.Value = DBNull.Value;
                }

                command.Parameters.Add(p);
            }
        }

        /**/
        /// <summary>
        /// 这个方法用来给一组参数对象赋值
        /// </summary>
        /// <param name="commandParameters">array of SqlParameters to be assigned values</param>
        /// <param name="parameterValues">array of objects holding the values to be assigned</param>
        public static void AssignParameterValues(SqlParameter[] commandParameters, params object[] parameterValues)
        {
            if ((commandParameters == null) || (parameterValues == null))
            {
                //do nothing if we get no data
                return;
            }

            // we must have the same number of values as we pave parameters to put them in
            if (commandParameters.Length != parameterValues.Length)
            {
                throw new ArgumentException("Parameter count does not match Parameter Value count.");
            }

            //iterate through the SqlParameters, assigning the values from the corresponding position in the
            //value array
            for (int i = 0, j = commandParameters.Length; i < j; i++)
            {
                if (parameterValues[i] != null && (commandParameters[i].Direction == ParameterDirection.Input || commandParameters[i].Direction == ParameterDirection.InputOutput))
                {
                    commandParameters[i].Value = parameterValues[i];
                }
            }
        }

        public static void AssignParameterValues(SqlParameter[] commandParameters, Hashtable parameterValues)
        {
            if ((commandParameters == null) || (parameterValues == null))
            {
                //do nothing if we get no data
                return;
            }

            // we must have the same number of values as we pave parameters to put them in
            if (commandParameters.Length != parameterValues.Count)
            {
                throw new ArgumentException("Parameter count does not match Parameter Value count.");
            }

            //iterate through the SqlParameters, assigning the values from the corresponding position in the
            //value array
            for (int i = 0, j = commandParameters.Length; i < j; i++)
            {
                if (parameterValues[commandParameters[i].ParameterName] != null && (commandParameters[i].Direction == ParameterDirection.Input || commandParameters[i].Direction == ParameterDirection.InputOutput))
                {
                    commandParameters[i].Value = parameterValues[commandParameters[i].ParameterName];
                }
            }
        }

        /**/
        /// <summary>
        /// This method opens (if necessary) and assigns a connection, transaction, command type and parameters
        /// to the provided command.
        /// </summary>
        /// <param name="command">the SqlCommand to be prepared</param>
        /// <param name="connection">a valid SqlConnection, on which to execute this command</param>
        /// <param name="transaction">a valid SqlTransaction, or 'null'</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParameters to be associated with the command or 'null' if no parameters are required</param>
        private static void PrepareCommand(SqlCommand command, SqlConnection connection, SqlTransaction transaction, CommandType commandType, string commandText, SqlParameter[] commandParameters)
        {
            //if the provided connection is not open, we will open it
            if (connection.State != ConnectionState.Open)
            {
                connection.Open();
            }

            //associate the connection with the command
            command.Connection = connection;

            //set the command text (stored procedure name or SQL statement)
            command.CommandText = commandText;

            //if we were provided a transaction, assign it.
            if (transaction != null)
            {
                command.Transaction = transaction;
            }

            //set the command type
            command.CommandType = commandType;

            //attach the command parameters if they are provided
            if (commandParameters != null)
            {
                AttachParameters(command, commandParameters);
            }

            return;
        }

        #endregion

        #region ExecuteNonQuery

        /**/
        /// <summary>
        /// 执行一个指定连接串上的一个SqlCommand（不返回记录集也没有任何参数）
        /// Execute a SqlCommand (that returns no resultset and takes no parameters) against the database specified in
        /// the connection string.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders");
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(string connectionString, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteNonQuery(connectionString, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// 执行一个指定连接串上的一个SqlCommand（不返回记录集），使用指定的参数集
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create & open a SqlConnection, and dispose of it after we are done.
            using (SqlConnection cn = new SqlConnection(connectionString))
            {
                cn.Open();

                //call the overload that takes a connection in place of the connection string
                return ExecuteNonQuery(cn, commandType, commandText, commandParameters);
            }
        }

        /**/
        /// <summary>
        /// 执行一个存储过程并赋值，这个方法将从数据库中获得存储过程的参数对象并根据其顺序赋值
        /// Execute a stored procedure via a SqlCommand (that returns no resultset) against the database specified in
        /// the connection string using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  int result = ExecuteNonQuery(connString, "PublishOrders", 24, 36);
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="spName">the name of the stored prcedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(string connectionString, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteNonQuery(connectionString, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteNonQuery(connectionString, CommandType.StoredProcedure, spName);
            }
        }

        public static int ExecuteNonQuery(string connectionString, string spName, Hashtable parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Count > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteNonQuery(connectionString, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteNonQuery(connectionString, CommandType.StoredProcedure, spName);
            }
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns no resultset and takes no parameters) against the provided SqlConnection.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int result = ExecuteNonQuery(conn, CommandType.StoredProcedure, "PublishOrders");
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(SqlConnection connection, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteNonQuery(connection, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns no resultset) against the specified SqlConnection
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int result = ExecuteNonQuery(conn, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters);

            //finally, execute the command.
            int retval = cmd.ExecuteNonQuery();

            // detach the SqlParameters from the command object, so they can be used again.
            cmd.Parameters.Clear();
            return retval;
        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns no resultset) against the specified SqlConnection
        /// using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  int result = ExecuteNonQuery(conn, "PublishOrders", 24, 36);
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(SqlConnection connection, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connection.ConnectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteNonQuery(connection, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteNonQuery(connection, CommandType.StoredProcedure, spName);
            }
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns no resultset and takes no parameters) against the provided SqlTransaction.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int result = ExecuteNonQuery(trans, CommandType.StoredProcedure, "PublishOrders");
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(SqlTransaction transaction, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteNonQuery(transaction, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns no resultset) against the specified SqlTransaction
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int result = ExecuteNonQuery(trans, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(SqlTransaction transaction, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, transaction.Connection, transaction, commandType, commandText, commandParameters);

            //finally, execute the command.
            int retval = cmd.ExecuteNonQuery();

            // detach the SqlParameters from the command object, so they can be used again.
            cmd.Parameters.Clear();
            return retval;
        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns no resultset) against the specified
        /// SqlTransaction using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  int result = ExecuteNonQuery(conn, trans, "PublishOrders", 24, 36);
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>an int representing the number of rows affected by the command</returns>
        public static int ExecuteNonQuery(SqlTransaction transaction, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(transaction.Connection.ConnectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteNonQuery(transaction, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteNonQuery(transaction, CommandType.StoredProcedure, spName);
            }
        }

        #endregion

        #region ExecuteDataSet

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset and takes no parameters) against the database specified in
        /// the connection string.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  DataSet ds = ExecuteDataset(connString, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>a dataset containing the resultset generated by the command</returns>
        public static DataSet ExecuteDataset(string connectionString, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteDataset(connectionString, commandType, commandText, (SqlParameter[])null);
        }
        //public static DataTable ExecuteDataTable(string connectionString, CommandType commandType, string commandText)
        //{
        //    return ExecuteDataTable(connectionString, commandType, commandText);
        //}

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset) against the database specified in the connection string
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  DataSet ds = ExecuteDataset(connString, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>a dataset containing the resultset generated by the command</returns>
        public static DataSet ExecuteDataset(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create & open a SqlConnection, and dispose of it after we are done.
            using (SqlConnection cn = new SqlConnection(connectionString))
            {
                cn.Open();

                //call the overload that takes a connection in place of the connection string
                return ExecuteDataset(cn, commandType, commandText, commandParameters);
            }
        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns a resultset) against the database specified in
        /// the connection string using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  DataSet ds = ExecuteDataset(connString, "GetOrders", 24, 36);
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>a dataset containing the resultset generated by the command</returns>
        public static DataSet ExecuteDataset(string connectionString, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteDataset(connectionString, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteDataset(connectionString, CommandType.StoredProcedure, spName);
            }
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset and takes no parameters) against the provided SqlConnection.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  DataSet ds = ExecuteDataset(conn, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>a dataset containing the resultset generated by the command</returns>
        public static DataSet ExecuteDataset(SqlConnection connection, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteDataset(connection, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset) against the specified SqlConnection
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  DataSet ds = ExecuteDataset(conn, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>a dataset containing the resultset generated by the command</returns>
        public static DataSet ExecuteDataset(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters);

            //create the DataAdapter & DataSet
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();

            //fill the DataSet using default values for DataTable names, etc.
            da.Fill(ds);

            // detach the SqlParameters from the command object, so they can be used again.           
            cmd.Parameters.Clear();

            //return the dataset
            return ds;
        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns a resultset) against the specified SqlConnection
        /// using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  DataSet ds = ExecuteDataset(conn, "GetOrders", 24, 36);
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>a dataset containing the resultset generated by the command</returns>
        public static DataSet ExecuteDataset(SqlConnection connection, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connection.ConnectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteDataset(connection, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteDataset(connection, CommandType.StoredProcedure, spName);
            }
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset and takes no parameters) against the provided SqlTransaction.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  DataSet ds = ExecuteDataset(trans, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>a dataset containing the resultset generated by the command</returns>
        public static DataSet ExecuteDataset(SqlTransaction transaction, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteDataset(transaction, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset) against the specified SqlTransaction
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  DataSet ds = ExecuteDataset(trans, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>a dataset containing the resultset generated by the command</returns>
        public static DataSet ExecuteDataset(SqlTransaction transaction, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, transaction.Connection, transaction, commandType, commandText, commandParameters);

            //create the DataAdapter & DataSet
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();

            //fill the DataSet using default values for DataTable names, etc.
            da.Fill(ds);

            // detach the SqlParameters from the command object, so they can be used again.
            cmd.Parameters.Clear();

            //return the dataset
            return ds;
        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns a resultset) against the specified
        /// SqlTransaction using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  DataSet ds = ExecuteDataset(trans, "GetOrders", 24, 36);
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>a dataset containing the resultset generated by the command</returns>
        public static DataSet ExecuteDataset(SqlTransaction transaction, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(transaction.Connection.ConnectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteDataset(transaction, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteDataset(transaction, CommandType.StoredProcedure, spName);
            }
        }

        #endregion

        #region ExecuteReader

        /**/
        /// <summary>
        /// this enum is used to indicate whether the connection was provided by the caller, or created by SqlHelper, so that
        /// we can set the appropriate CommandBehavior when calling ExecuteReader()
        /// </summary>
        private enum SqlConnectionOwnership
        {
            /**/
            /// <summary>Connection is owned and managed by SqlHelper</summary>
            Internal,
            /**/
            /// <summary>Connection is owned and managed by the caller</summary>
            External
        }

        /**/
        /// <summary>
        /// Create and prepare a SqlCommand, and call ExecuteReader with the appropriate CommandBehavior.
        /// </summary>
        /// <remarks>
        /// If we created and opened the connection, we want the connection to be closed when the DataReader is closed.
        ///
        /// If the caller provided the connection, we want to leave it to them to manage.
        /// </remarks>
        /// <param name="connection">a valid SqlConnection, on which to execute this command</param>
        /// <param name="transaction">a valid SqlTransaction, or 'null'</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParameters to be associated with the command or 'null' if no parameters are required</param>
        /// <param name="connectionOwnership">indicates whether the connection parameter was provided by the caller, or created by SqlHelper</param>
        /// <returns>SqlDataReader containing the results of the command</returns>
        private static SqlDataReader ExecuteReader(SqlConnection connection, SqlTransaction transaction, CommandType commandType, string commandText, SqlParameter[] commandParameters, SqlConnectionOwnership connectionOwnership)
        {
            //create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, connection, transaction, commandType, commandText, commandParameters);

            //create a reader
            SqlDataReader dr;

            // call ExecuteReader with the appropriate CommandBehavior
            if (connectionOwnership == SqlConnectionOwnership.External)
            {
                dr = cmd.ExecuteReader();
            }
            else
            {
                dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
            }

            // detach the SqlParameters from the command object, so they can be used again.
            cmd.Parameters.Clear();

            return dr;
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset and takes no parameters) against the database specified in
        /// the connection string.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  SqlDataReader dr = ExecuteReader(connString, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>a SqlDataReader containing the resultset generated by the command</returns>
        public static SqlDataReader ExecuteReader(string connectionString, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteReader(connectionString, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset) against the database specified in the connection string
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  SqlDataReader dr = ExecuteReader(connString, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>a SqlDataReader containing the resultset generated by the command</returns>
        public static SqlDataReader ExecuteReader(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create & open a SqlConnection
            SqlConnection cn = new SqlConnection(connectionString);
            cn.Open();

            try
            {
                //call the private overload that takes an internally owned connection in place of the connection string
                return ExecuteReader(cn, null, commandType, commandText, commandParameters, SqlConnectionOwnership.Internal);
            }
            catch
            {
                //if we fail to return the SqlDatReader, we need to close the connection ourselves
                cn.Close();
                throw;
            }
        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns a resultset) against the database specified in
        /// the connection string using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  SqlDataReader dr = ExecuteReader(connString, "GetOrders", 24, 36);
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>a SqlDataReader containing the resultset generated by the command</returns>
        public static SqlDataReader ExecuteReader(string connectionString, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteReader(connectionString, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteReader(connectionString, CommandType.StoredProcedure, spName);
            }
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset and takes no parameters) against the provided SqlConnection.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  SqlDataReader dr = ExecuteReader(conn, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>a SqlDataReader containing the resultset generated by the command</returns>
        public static SqlDataReader ExecuteReader(SqlConnection connection, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteReader(connection, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset) against the specified SqlConnection
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  SqlDataReader dr = ExecuteReader(conn, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>a SqlDataReader containing the resultset generated by the command</returns>
        public static SqlDataReader ExecuteReader(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //pass through the call to the private overload using a null transaction value and an externally owned connection
            return ExecuteReader(connection, (SqlTransaction)null, commandType, commandText, commandParameters, SqlConnectionOwnership.External);
        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns a resultset) against the specified SqlConnection
        /// using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  SqlDataReader dr = ExecuteReader(conn, "GetOrders", 24, 36);
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>a SqlDataReader containing the resultset generated by the command</returns>
        public static SqlDataReader ExecuteReader(SqlConnection connection, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connection.ConnectionString, spName);

                AssignParameterValues(commandParameters, parameterValues);

                return ExecuteReader(connection, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteReader(connection, CommandType.StoredProcedure, spName);
            }
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset and takes no parameters) against the provided SqlTransaction.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  SqlDataReader dr = ExecuteReader(trans, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>a SqlDataReader containing the resultset generated by the command</returns>
        public static SqlDataReader ExecuteReader(SqlTransaction transaction, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteReader(transaction, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset) against the specified SqlTransaction
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///   SqlDataReader dr = ExecuteReader(trans, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>a SqlDataReader containing the resultset generated by the command</returns>
        public static SqlDataReader ExecuteReader(SqlTransaction transaction, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //pass through to private overload, indicating that the connection is owned by the caller
            return ExecuteReader(transaction.Connection, transaction, commandType, commandText, commandParameters, SqlConnectionOwnership.External);
        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns a resultset) against the specified
        /// SqlTransaction using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  SqlDataReader dr = ExecuteReader(trans, "GetOrders", 24, 36);
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>a SqlDataReader containing the resultset generated by the command</returns>
        public static SqlDataReader ExecuteReader(SqlTransaction transaction, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(transaction.Connection.ConnectionString, spName);

                AssignParameterValues(commandParameters, parameterValues);

                return ExecuteReader(transaction, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteReader(transaction, CommandType.StoredProcedure, spName);
            }
        }

        #endregion

        #region ExecuteScalar

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a 1x1 resultset and takes no parameters) against the database specified in
        /// the connection string.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int orderCount = (int)ExecuteScalar(connString, CommandType.StoredProcedure, "GetOrderCount");
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
        public static object ExecuteScalar(string connectionString, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteScalar(connectionString, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a 1x1 resultset) against the database specified in the connection string
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int orderCount = (int)ExecuteScalar(connString, CommandType.StoredProcedure, "GetOrderCount", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
        public static object ExecuteScalar(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create & open a SqlConnection, and dispose of it after we are done.
            using (SqlConnection cn = new SqlConnection(connectionString))
            {
                cn.Open();

                //call the overload that takes a connection in place of the connection string
                return ExecuteScalar(cn, commandType, commandText, commandParameters);
            }
        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns a 1x1 resultset) against the database specified in
        /// the connection string using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  int orderCount = (int)ExecuteScalar(connString, "GetOrderCount", 24, 36);
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
        public static object ExecuteScalar(string connectionString, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteScalar(connectionString, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteScalar(connectionString, CommandType.StoredProcedure, spName);
            }
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a 1x1 resultset and takes no parameters) against the provided SqlConnection.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int orderCount = (int)ExecuteScalar(conn, CommandType.StoredProcedure, "GetOrderCount");
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
        public static object ExecuteScalar(SqlConnection connection, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteScalar(connection, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a 1x1 resultset) against the specified SqlConnection
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int orderCount = (int)ExecuteScalar(conn, CommandType.StoredProcedure, "GetOrderCount", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
        public static object ExecuteScalar(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters);

            //execute the command & return the results
            object retval = cmd.ExecuteScalar();

            // detach the SqlParameters from the command object, so they can be used again.
            cmd.Parameters.Clear();
            return retval;

        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns a 1x1 resultset) against the specified SqlConnection
        /// using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  int orderCount = (int)ExecuteScalar(conn, "GetOrderCount", 24, 36);
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
        public static object ExecuteScalar(SqlConnection connection, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connection.ConnectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteScalar(connection, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteScalar(connection, CommandType.StoredProcedure, spName);
            }
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a 1x1 resultset and takes no parameters) against the provided SqlTransaction.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int orderCount = (int)ExecuteScalar(trans, CommandType.StoredProcedure, "GetOrderCount");
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
        public static object ExecuteScalar(SqlTransaction transaction, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteScalar(transaction, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a 1x1 resultset) against the specified SqlTransaction
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  int orderCount = (int)ExecuteScalar(trans, CommandType.StoredProcedure, "GetOrderCount", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
        public static object ExecuteScalar(SqlTransaction transaction, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, transaction.Connection, transaction, commandType, commandText, commandParameters);

            //execute the command & return the results
            object retval = cmd.ExecuteScalar();

            // detach the SqlParameters from the command object, so they can be used again.
            cmd.Parameters.Clear();
            return retval;
        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns a 1x1 resultset) against the specified
        /// SqlTransaction using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  int orderCount = (int)ExecuteScalar(trans, "GetOrderCount", 24, 36);
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>an object containing the value in the 1x1 resultset generated by the command</returns>
        public static object ExecuteScalar(SqlTransaction transaction, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(transaction.Connection.ConnectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteScalar(transaction, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteScalar(transaction, CommandType.StoredProcedure, spName);
            }
        }

        #endregion

        #region ExecuteXmlReader

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset and takes no parameters) against the provided SqlConnection.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  XmlReader r = ExecuteXmlReader(conn, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command using "FOR XML AUTO"</param>
        /// <returns>an XmlReader containing the resultset generated by the command</returns>
        public static XmlReader ExecuteXmlReader(SqlConnection connection, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteXmlReader(connection, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset) against the specified SqlConnection
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  XmlReader r = ExecuteXmlReader(conn, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command using "FOR XML AUTO"</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>an XmlReader containing the resultset generated by the command</returns>
        public static XmlReader ExecuteXmlReader(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters);

            //create the DataAdapter & DataSet
            XmlReader retval = cmd.ExecuteXmlReader();

            // detach the SqlParameters from the command object, so they can be used again.
            cmd.Parameters.Clear();
            return retval;

        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns a resultset) against the specified SqlConnection
        /// using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  XmlReader r = ExecuteXmlReader(conn, "GetOrders", 24, 36);
        /// </remarks>
        /// <param name="connection">a valid SqlConnection</param>
        /// <param name="spName">the name of the stored procedure using "FOR XML AUTO"</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>an XmlReader containing the resultset generated by the command</returns>
        public static XmlReader ExecuteXmlReader(SqlConnection connection, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connection.ConnectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteXmlReader(connection, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteXmlReader(connection, CommandType.StoredProcedure, spName);
            }
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset and takes no parameters) against the provided SqlTransaction.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  XmlReader r = ExecuteXmlReader(trans, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command using "FOR XML AUTO"</param>
        /// <returns>an XmlReader containing the resultset generated by the command</returns>
        public static XmlReader ExecuteXmlReader(SqlTransaction transaction, CommandType commandType, string commandText)
        {
            //pass through the call providing null for the set of SqlParameters
            return ExecuteXmlReader(transaction, commandType, commandText, (SqlParameter[])null);
        }

        /**/
        /// <summary>
        /// Execute a SqlCommand (that returns a resultset) against the specified SqlTransaction
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.: 
        ///  XmlReader r = ExecuteXmlReader(trans, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command using "FOR XML AUTO"</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>an XmlReader containing the resultset generated by the command</returns>
        public static XmlReader ExecuteXmlReader(SqlTransaction transaction, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, transaction.Connection, transaction, commandType, commandText, commandParameters);

            //create the DataAdapter & DataSet
            XmlReader retval = cmd.ExecuteXmlReader();

            // detach the SqlParameters from the command object, so they can be used again.
            cmd.Parameters.Clear();
            return retval;
        }

        /**/
        /// <summary>
        /// Execute a stored procedure via a SqlCommand (that returns a resultset) against the specified
        /// SqlTransaction using the provided parameter values.  This method will query the database to discover the parameters for the
        /// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
        /// </summary>
        /// <remarks>
        /// This method provides no access to output parameters or the stored procedure's return value parameter.
        ///
        /// e.g.: 
        ///  XmlReader r = ExecuteXmlReader(trans, "GetOrders", 24, 36);
        /// </remarks>
        /// <param name="transaction">a valid SqlTransaction</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="parameterValues">an array of objects to be assigned as the input values of the stored procedure</param>
        /// <returns>a dataset containing the resultset generated by the command</returns>
        public static XmlReader ExecuteXmlReader(SqlTransaction transaction, string spName, params object[] parameterValues)
        {
            //if we receive parameter values, we need to figure out where they go
            if ((parameterValues != null) && (parameterValues.Length > 0))
            {
                //pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(transaction.Connection.ConnectionString, spName);

                //assign the provided values to these parameters based on parameter order
                AssignParameterValues(commandParameters, parameterValues);

                //call the overload that takes an array of SqlParameters
                return ExecuteXmlReader(transaction, CommandType.StoredProcedure, spName, commandParameters);
            }
            //otherwise we can just call the SP without params
            else
            {
                return ExecuteXmlReader(transaction, CommandType.StoredProcedure, spName);
            }
        }

        #endregion
    }

    /**/
    /// <summary>
    /// SqlHelperParameterCache provides functions to leverage a static cache of procedure parameters, and the
    /// ability to discover parameters for stored procedures at run-time.
    /// SqlHelperParameterCache支持函数来实现静态缓存存储过程参数，并支持在运行时得到存储过程的参数
    /// </summary>
    public class SqlHelperParameterCache
    {
        #region private methods, variables, and constructors

        //Since this class provides only static methods, make the default constructor private to prevent
        //instances from being created with "new SqlHelperParameterCache()".
        //类提供的都是静态方法，将默认构造函数设置为私有的以便阻止利用"new SqlHelperParameterCache()"来实例化类
        private SqlHelperParameterCache() { }

        //存储过程参数缓存导HashTable中
        private static Hashtable paramCache = Hashtable.Synchronized(new Hashtable());

        /**/
        /// <summary>
        /// resolve at run time the appropriate set of SqlParameters for a stored procedure
        /// 在运行时得到一个存储过程的一系列参数信息
        /// </summary>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="connectionString">一个连接对象的有效连接串</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="spName">存储过程名</param>
        /// <param name="includeReturnValueParameter">是否有返回值参数</param>
        /// <returns>参数对象数组，存储过程的所有参数信息</returns>
        private static SqlParameter[] DiscoverSpParameterSet(string connectionString, string spName, bool includeReturnValueParameter)
        {
            using (SqlConnection cn = new SqlConnection(connectionString))
            using (SqlCommand cmd = new SqlCommand(spName, cn))
            {
                cn.Open();
                cmd.CommandType = CommandType.StoredProcedure;

                //从 SqlCommand 指定的存储过程中检索参数信息，并填充指定的 SqlCommand 对象的 Parameters 集。
                SqlCommandBuilder.DeriveParameters(cmd);

                if (!includeReturnValueParameter)
                {
                    //移除第一个参数对象，因为没有返回值，而默认情况下，第一个参数对象是返回值
                    cmd.Parameters.RemoveAt(0);
                }

                SqlParameter[] discoveredParameters = new SqlParameter[cmd.Parameters.Count]; ;

                cmd.Parameters.CopyTo(discoveredParameters, 0);

                return discoveredParameters;
            }
        }

        //deep copy of cached SqlParameter array
        //复制缓存参数数组（克隆）
        private static SqlParameter[] CloneParameters(SqlParameter[] originalParameters)
        {
            SqlParameter[] clonedParameters = new SqlParameter[originalParameters.Length];

            for (int i = 0, j = originalParameters.Length; i < j; i++)
            {
                clonedParameters[i] = (SqlParameter)((ICloneable)originalParameters[i]).Clone();
            }

            return clonedParameters;
        }

        #endregion

        #region caching functions

        /**/
        /// <summary>
        /// 将参数数组添加到缓存中
        /// </summary>
        /// <param name="connectionString">有效的连接串</param>
        /// <param name="commandText">一个存储过程名或者T-SQL命令</param>
        /// <param name="commandParameters">一个要被缓存的参数对象数组</param>
        public static void CacheParameterSet(string connectionString, string commandText, params SqlParameter[] commandParameters)
        {
            string hashKey = connectionString + ":" + commandText;

            paramCache[hashKey] = commandParameters;
        }

        /**/
        /// <summary>
        /// 从缓存中获得参数对象数组
        /// </summary>
        /// <param name="connectionString">有效的连接串</param>
        /// <param name="commandText">一个存储过程名或者T-SQL命令</param>
        /// <returns>一个参数对象数组</returns>
        public static SqlParameter[] GetCachedParameterSet(string connectionString, string commandText)
        {
            string hashKey = connectionString + ":" + commandText;

            SqlParameter[] cachedParameters = (SqlParameter[])paramCache[hashKey];

            if (cachedParameters == null)
            {
                return null;
            }
            else
            {
                return CloneParameters(cachedParameters);
            }
        }

        #endregion

        #region Parameter Discovery Functions

        /**/
        /// <summary>
        /// 获得存储过程的参数集
        /// </summary>
        /// <remarks>
        /// 这个方法从数据库中获得信息，并将之存储在缓存，以便之后的使用
        /// </remarks>
        /// <param name="connectionString">有效的连接串</param>
        /// <param name="commandText">一个存储过程名或者T-SQL命令</param>
        /// <returns>一个参数对象数组</returns>
        public static SqlParameter[] GetSpParameterSet(string connectionString, string spName)
        {
            return GetSpParameterSet(connectionString, spName, false);
        }

        /**/
        /// <summary>
        /// 获得存储过程的参数集
        /// </summary>
        /// <remarks>
        /// 这个方法从数据库中获得信息，并将之存储在缓存，以便之后的使用
        /// </remarks>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="spName">the name of the stored procedure</param>
        /// <param name="includeReturnValueParameter">a bool value indicating whether the return value parameter should be included in the results</param>
        /// <returns>an array of SqlParameters</returns>
        /// <param name="connectionString">有效的连接串</param>
        /// <param name="commandText">一个存储过程名</param>
        /// /// <param name="includeReturnValueParameter">是否有返回值参数</param>
        /// <returns>一个参数对象数组</returns>
        public static SqlParameter[] GetSpParameterSet(string connectionString, string spName, bool includeReturnValueParameter)
        {
            string hashKey = connectionString + ":" + spName + (includeReturnValueParameter ? ":include ReturnValue Parameter" : "");

            SqlParameter[] cachedParameters;

            cachedParameters = (SqlParameter[])paramCache[hashKey];

            if (cachedParameters == null)
            {
                cachedParameters = (SqlParameter[])(paramCache[hashKey] = DiscoverSpParameterSet(connectionString, spName, includeReturnValueParameter));
            }

            return CloneParameters(cachedParameters);
        }

        #endregion Parameter Discovery Functions

    }
}