DBcommand 、DBconnection对象的使用示例。

// Takes a DbConnection and creates a DbCommand to retrieve data
// from the Categories table by executing a DbDataReader.
static void DbCommandSelect(DbConnection connection)
{
    string queryString =
        "SELECT CategoryID, CategoryName FROM Categories";

    // Check for valid DbConnection.
    if (connection != null)
    {
        using (connection)
        {
            try
            {
                // Create the command.
                DbCommand command = connection.CreateCommand();
                command.CommandText = queryString;
                command.CommandType = CommandType.Text;

                // Open the connection.
                connection.Open();

                // Retrieve the data.
                DbDataReader reader = command.ExecuteReader();
                while (reader.Read())
                {
                    Console.WriteLine("{0}. {1}", reader[0], reader[1]);
                }
            }

            catch (Exception ex)
            {
                Console.WriteLine("Exception.Message: {0}", ex.Message);
            }
        }
    }
    else
    {
        Console.WriteLine("Failed: DbConnection is null.");
    }
}