ADO.NET 连接数据库的另一种方法（通过配置文件和基类转化，适用于后期维护）

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本文参考C#高级编程（第七版）30.2

首先是书上一个简单的数据库连接的demo

using System;using System.Data.SqlClient;public class ExecuteNonQueryExample{   public static void Main(string[] args)   {      string source = "server=(local);" +                      "integrated security=SSPI;" +                      "database=Northwind";      string select = "UPDATE Customers " +                      "SET ContactName = 'Bob' " +                      "WHERE ContactName = 'Bill'";      SqlConnection  conn = new SqlConnection(source);      conn.Open();      SqlCommand cmd = new SqlCommand(select, conn);      int rowsReturned = cmd.ExecuteNonQuery();      Console.WriteLine("{0} rows returned.", rowsReturned);      conn.Close();   }}

为了方便管理连接数据库，更为了后期维护的方便。采用另外一种方式

将数据库的的配置信息放到配置文件（app.config）中，如下

<?xml version="1.0" encoding="utf-8" ?><configuration>  <connectionStrings>    <add name="db"         providerName="System.Data.SqlClient"         connectionString="server=(local)\SQLEXPRESS;integrated security=SSPI;database=test;" />  </connectionStrings></configuration>

其次为了让适用于各种类型的数据库，将连接方式专门新建一个静态类，命名databases.cs

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Data.Common;using System.Configuration;namespace ConsoleApplication1{    static class databases    {        static public DbConnection GetDatabaseConnection(string name)        {            ConnectionStringSettings settings =              ConfigurationManager.ConnectionStrings[name];            DbProviderFactory factory = DbProviderFactories.GetFactory(settings.ProviderName);            DbConnection conn = factory.CreateConnection();            conn.ConnectionString = settings.ConnectionString;            return conn;        }    }}

如果出现 ConnectionStringSettings 无法识别的情况，需要在解决方案的那里引用一个System.Configuration

那么新的数据库操作方式就是

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Data.SqlClient;using System.Data.Common;namespace ConsoleApplication1{    class Program    {        static void Main(string[] args)        {            string select = "insert into person(name,sex) values('bb','sb')";            try            {                //返回DbConnection类型的连接，强制转换成SqlConnection类型，SqlConnection用以连接sql server数据库                using (SqlConnection conn = (SqlConnection)databases.GetDatabaseConnection("db"))                {                    conn.Open();                    SqlCommand cmd = new SqlCommand(select, conn);                    int rowsReturned = cmd.ExecuteNonQuery();                    Console.WriteLine("{0} rows returned.", rowsReturned);                    conn.Close();                    Console.ReadLine();                }                //useing的对象在结束后会自动销毁对象。            }            catch(SqlException e)            {                throw e;            }       }    }}

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