微软SQLHelper类，含中文注释

using System;
using System.Data;
using System.Xml;
using System.Data.SqlClient;
using System.Collections;
namespace myhelper
{
    /// <summary>
    /// SqlServer数据访问帮助类
    /// </summary>
    public sealed class SqlHelper
    {
        #region 私有构造函数和方法
        private SqlHelper() {}
        /// <summary>
        /// 将SqlParameter参数数组(参数值)分配给SqlCommand命令.
        /// 这个方法将给任何一个参数分配DBNull.Value;
        /// 该操作将阻止默认值的使用.
        /// </summary>SqlHelperSqlHelper
        /// <param>命令名</param>
        /// <param>SqlParameters数组</param>
        private static void AttachParameters(SqlCommand command, SqlParameter[] commandParameters)
        {
            if( command == null ) throw new ArgumentNullException( "command" );
            if( commandParameters != null )
            {
                foreach (SqlParameter p in commandParameters)
                {
                    if( p != null )
                    {
                        // 检查未分配值的输出参数,将其分配以DBNull.Value.
                        if ( ( p.Direction == ParameterDirection.InputOutput || p.Direction == ParameterDirection.Input ) && 
                            (p.Value == null))
                        {
                            p.Value = DBNull.Value;
                        }
                        command.Parameters.Add(p);
                    }
                }
            }
        }
        
        /// <summary>
        /// 将DataRow类型的列值分配到SqlParameter参数数组.
        /// </summary>
        /// <param>要分配值的SqlParameter参数数组</param>
        /// <param>将要分配给存储过程参数的DataRow</param>
        private static void AssignParameterValues(SqlParameter[] commandParameters, DataRow dataRow)
        {
            if ((commandParameters == null) || (dataRow == null)) 
            {
                return;
            }
            int i = 0;
            // 设置参数值
            foreach(SqlParameter commandParameter in commandParameters)
            {
                // 创建参数名称,如果不存在,只抛出一个异常.
                if( commandParameter.ParameterName == null || 
                    commandParameter.ParameterName.Length <= 1 )
                    throw new Exception( 
                        string.Format("请提供参数{0}一个有效的名称{1}.", i, commandParameter.ParameterName ) );
                // 从dataRow的表中获取为参数数组中数组名称的列的索引.
                // 如果存在和参数名称相同的列,则将列值赋给当前名称的参数.
                if (dataRow.Table.Columns.IndexOf(commandParameter.ParameterName.Substring(1)) != -1)
                    commandParameter.Value = dataRow[commandParameter.ParameterName.Substring(1)];
                i++;
            }
        }
        
        /// <summary>
        /// 将一个对象数组分配给SqlParameter参数数组.
        /// </summary>
        /// <param>要分配值的SqlParameter参数数组</param>
        /// <param>将要分配给存储过程参数的对象数组</param>
        private static void AssignParameterValues(SqlParameter[] commandParameters, object[] parameterValues)
        {
            if ((commandParameters == null) || (parameterValues == null)) 
            {
                return;
            }
            // 确保对象数组个数与参数个数匹配,如果不匹配,抛出一个异常.
            if (commandParameters.Length != parameterValues.Length)
            {
                throw new ArgumentException("参数值个数与参数不匹配.");
            }
            // 给参数赋值
            for (int i = 0, j = commandParameters.Length; i < j; i++)
            {
                // If the current array value derives from IDbDataParameter, then assign its Value property
                if (parameterValues is IDbDataParameter)
                {
                    IDbDataParameter paramInstance = (IDbDataParameter)parameterValues;
                    if( paramInstance.Value == null )
                    {
                        commandParameters.Value = DBNull.Value; 
                    }
                    else
                    {
                        commandParameters.Value = paramInstance.Value;
                    }
                }
                else if (parameterValues == null)
                {
                    commandParameters.Value = DBNull.Value;
                }
                else
                {
                    commandParameters.Value = parameterValues;
                }
            }
        }
        
        /// <summary>
        /// 预处理用户提供的命令,数据库连接/事务/命令类型/参数
        /// </summary>
        /// <param>要处理的SqlCommand</param>
        /// <param>数据库连接</param>
        /// <param>一个有效的事务或者是null值</param>
        /// <param>命令类型 (存储过程,命令文本, 其它.)</param>
        /// <param>存储过程名或都T-SQL命令文本</param>
        /// <param>和命令相关联的SqlParameter参数数组,如果没有参数为‘null‘</param>
        /// <param><c>true</c> 如果连接是打开的,则为true,其它情况下为false.</param>
        private static void PrepareCommand(SqlCommand command, SqlConnection connection, SqlTransaction transaction, CommandType commandType, string commandText, SqlParameter[] commandParameters, out bool mustCloseConnection )
        {
            if( command == null ) throw new ArgumentNullException( "command" );
            if( commandText == null || commandText.Length == 0 ) throw new ArgumentNullException( "commandText" );
            // If the provided connection is not open, we will open it
            if (connection.State != ConnectionState.Open)
            {
                mustCloseConnection = true;
                connection.Open();
            }
            else
            {
                mustCloseConnection = false;
            }
            // 给命令分配一个数据库连接.
            command.Connection = connection;
            // 设置命令文本(存储过程名或SQL语句)
            command.CommandText = commandText;
            // 分配事务
            if (transaction != null)
            {
                if( transaction.Connection == null ) throw new ArgumentException( "The transaction was rollbacked or commited, please provide an open transaction.", "transaction" );
                command.Transaction = transaction;
            }
            // 设置命令类型.
            command.CommandType = commandType;
            // 分配命令参数
            if (commandParameters != null)
            {
                AttachParameters(command, commandParameters);
            }
            return;
        }
        #endregion 私有构造函数和方法结束
            
        #region ExecuteNonQuery命令
        /// <summary>
        /// 执行指定连接字符串,类型的SqlCommand.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders");
        /// </remarks>
        /// <param>一个有效的数据库连接字符串</param>
        /// <param>命令类型 (存储过程,命令文本, 其它.)</param>
        /// <param>存储过程名称或SQL语句</param>
        /// <returns>返回命令影响的行数</returns>
        public static int ExecuteNonQuery(string connectionString, CommandType commandType, string commandText)
        {
            return ExecuteNonQuery(connectionString, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// 执行指定连接字符串,类型的SqlCommand.如果没有提供参数,不返回结果.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的数据库连接字符串</param>
        /// <param>命令类型 (存储过程,命令文本, 其它.)</param>
        /// <param>存储过程名称或SQL语句</param>
        /// <param>SqlParameter参数数组</param>
        /// <returns>返回命令影响的行数</returns>
        public static int ExecuteNonQuery(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if( connectionString == null || connectionString.Length == 0 ) throw new ArgumentNullException( "connectionString" );
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();
                return ExecuteNonQuery(connection, commandType, commandText, commandParameters);
            }
        }
        
        /// <summary>
        /// 执行指定连接字符串的存储过程,将对象数组的值赋给存储过程参数,
        /// 此方法需要在参数缓存方法中探索参数并生成参数.
        /// </summary>
        /// <remarks>
        /// 这个方法没有提供访问输出参数和返回值.
        /// 示例:  
        ///  int result = ExecuteNonQuery(connString, "PublishOrders", 24, 36);
        /// </remarks>
        /// <param>一个有效的数据库连接字符串/param>
        /// <param>存储过程名称</param>
        /// <param>分配到存储过程输入参数的对象数组</param>
        /// <returns>返回受影响的行数</returns>
        public static int ExecuteNonQuery(string connectionString, string spName, params object[] parameterValues)
        {
            if( connectionString == null || connectionString.Length == 0 ) throw new ArgumentNullException( "connectionString" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            // 如果存在参数值
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                // 从探索存储过程参数(加载到缓存)并分配给存储过程参数数组.
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);
                // 给存储过程参数赋值
                AssignParameterValues(commandParameters, parameterValues);
                return ExecuteNonQuery(connectionString, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                // 没有参数情况下
                return ExecuteNonQuery(connectionString, CommandType.StoredProcedure, spName);
            }
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的命令 
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  int result = ExecuteNonQuery(conn, CommandType.StoredProcedure, "PublishOrders");
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型(存储过程,命令文本或其它.)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <returns>返回影响的行数</returns>
        public static int ExecuteNonQuery(SqlConnection connection, CommandType commandType, string commandText)
        {
            return ExecuteNonQuery(connection, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的命令
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  int result = ExecuteNonQuery(conn, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型(存储过程,命令文本或其它.)</param>
        /// <param>T存储过程名称或T-SQL语句</param>
        /// <param>SqlParamter参数数组</param>
        /// <returns>返回影响的行数</returns>
        public static int ExecuteNonQuery(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {    
            if( connection == null ) throw new ArgumentNullException( "connection" );
            // 创建SqlCommand命令,并进行预处理
            SqlCommand cmd = new SqlCommand();
            bool mustCloseConnection = false;
            PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters, out mustCloseConnection );
            
            // Finally, execute the command
            int retval = cmd.ExecuteNonQuery();
            
            // 清除参数,以便再次使用.
            cmd.Parameters.Clear();
            if( mustCloseConnection )
                connection.Close();
            return retval;
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的命令,将对象数组的值赋给存储过程参数.
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输出参数和返回值
        /// 示例:  
        ///  int result = ExecuteNonQuery(conn, "PublishOrders", 24, 36);
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>存储过程名</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回影响的行数</returns>
        public static int ExecuteNonQuery(SqlConnection connection, string spName, params object[] parameterValues)
        {
            if( connection == null ) throw new ArgumentNullException( "connection" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            // 如果有参数值
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                // 从缓存中加载存储过程参数
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connection, spName);
                // 给存储过程分配参数值
                AssignParameterValues(commandParameters, parameterValues);
                return ExecuteNonQuery(connection, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                return ExecuteNonQuery(connection, CommandType.StoredProcedure, spName);
            }
        }
        
        /// <summary>
        /// 执行带事务的SqlCommand.
        /// </summary>
        /// <remarks>
        /// 示例.:  
        ///  int result = ExecuteNonQuery(trans, CommandType.StoredProcedure, "PublishOrders");
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型(存储过程,命令文本或其它.)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <returns>返回影响的行数/returns>
        public static int ExecuteNonQuery(SqlTransaction transaction, CommandType commandType, string commandText)
        {
            return ExecuteNonQuery(transaction, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// 执行带事务的SqlCommand(指定参数).
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  int result = ExecuteNonQuery(trans, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型(存储过程,命令文本或其它.)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <param>SqlParamter参数数组</param>
        /// <returns>返回影响的行数</returns>
        public static int ExecuteNonQuery(SqlTransaction transaction, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if( transaction == null ) throw new ArgumentNullException( "transaction" );
            if( transaction != null && transaction.Connection == null ) throw new ArgumentException( "The transaction was rollbacked or commited, please provide an open transaction.", "transaction" );
            // 预处理
            SqlCommand cmd = new SqlCommand();
            bool mustCloseConnection = false;
            PrepareCommand(cmd, transaction.Connection, transaction, commandType, commandText, commandParameters, out mustCloseConnection );
                
            // 执行
            int retval = cmd.ExecuteNonQuery();
                
            // 清除参数集,以便再次使用.
            cmd.Parameters.Clear();
            return retval;
        }
        
        /// <summary>
        /// 执行带事务的SqlCommand(指定参数值).
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输出参数和返回值
        /// 示例:  
        ///  int result = ExecuteNonQuery(conn, trans, "PublishOrders", 24, 36);
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>存储过程名</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回受影响的行数</returns>
        public static int ExecuteNonQuery(SqlTransaction transaction, string spName, params object[] parameterValues)
        {
            if( transaction == null ) throw new ArgumentNullException( "transaction" );
            if( transaction != null && transaction.Connection == null ) throw new ArgumentException( "The transaction was rollbacked or commited, please provide an open transaction.", "transaction" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            // 如果有参数值
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                // 从缓存中加载存储过程参数,如果缓存中不存在则从数据库中检索参数信息并加载到缓存中. ()
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(transaction.Connection, spName);
                // 给存储过程参数赋值
                AssignParameterValues(commandParameters, parameterValues);
                // 调用重载方法
                return ExecuteNonQuery(transaction, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                // 没有参数值
                return ExecuteNonQuery(transaction, CommandType.StoredProcedure, spName);
            }
        }
        #endregion ExecuteNonQuery方法结束
            
        #region ExecuteDataset方法
        /// <summary>
        /// 执行指定数据库连接字符串的命令,返回DataSet.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  DataSet ds = ExecuteDataset(connString, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param>一个有效的数据库连接字符串</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <returns>返回一个包含结果集的DataSet</returns>
        public static DataSet ExecuteDataset(string connectionString, CommandType commandType, string commandText)
        {
            return ExecuteDataset(connectionString, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// 执行指定数据库连接字符串的命令,返回DataSet.
        /// </summary>
        /// <remarks>
        /// 示例: 
        ///  DataSet ds = ExecuteDataset(connString, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的数据库连接字符串</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <param>SqlParamters参数数组</param>
        /// <returns>返回一个包含结果集的DataSet</returns>
        public static DataSet ExecuteDataset(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if( connectionString == null || connectionString.Length == 0 ) throw new ArgumentNullException( "connectionString" );
            // 创建并打开数据库连接对象,操作完成释放对象.
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();
                // 调用指定数据库连接字符串重载方法.
                return ExecuteDataset(connection, commandType, commandText, commandParameters);
            }
        }
        
        /// <summary>
        /// 执行指定数据库连接字符串的命令,直接提供参数值,返回DataSet.
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输出参数和返回值.
        /// 示例: 
        ///  DataSet ds = ExecuteDataset(connString, "GetOrders", 24, 36);
        /// </remarks>
        /// <param>一个有效的数据库连接字符串</param>
        /// <param>存储过程名</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回一个包含结果集的DataSet</returns>
        public static DataSet ExecuteDataset(string connectionString, string spName, params object[] parameterValues)
        {
            if( connectionString == null || connectionString.Length == 0 ) throw new ArgumentNullException( "connectionString" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                // 从缓存中检索存储过程参数
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);
                // 给存储过程参数分配值
                AssignParameterValues(commandParameters, parameterValues);
                return ExecuteDataset(connectionString, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                return ExecuteDataset(connectionString, CommandType.StoredProcedure, spName);
            }
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的命令,返回DataSet.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  DataSet ds = ExecuteDataset(conn, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名或T-SQL语句</param>
        /// <returns>返回一个包含结果集的DataSet</returns>
        public static DataSet ExecuteDataset(SqlConnection connection, CommandType commandType, string commandText)
        {
            return ExecuteDataset(connection, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的命令,指定存储过程参数,返回DataSet.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  DataSet ds = ExecuteDataset(conn, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名或T-SQL语句</param>
        /// <param>SqlParamter参数数组</param>
        /// <returns>返回一个包含结果集的DataSet</returns>
        public static DataSet ExecuteDataset(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if( connection == null ) throw new ArgumentNullException( "connection" );
            // 预处理
            SqlCommand cmd = new SqlCommand();
            bool mustCloseConnection = false;
            PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters, out mustCloseConnection );
                
            // 创建SqlDataAdapter和DataSet.
            using( SqlDataAdapter da = new SqlDataAdapter(cmd) )
            {
                DataSet ds = new DataSet();
                // 填充DataSet.
                da.Fill(ds);
                
                cmd.Parameters.Clear();
                if( mustCloseConnection )
                    connection.Close();
                return ds;
            }    
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的命令,指定参数值,返回DataSet.
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输入参数和返回值.
        /// 示例.:  
        ///  DataSet ds = ExecuteDataset(conn, "GetOrders", 24, 36);
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>存储过程名</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回一个包含结果集的DataSet</returns>
        public static DataSet ExecuteDataset(SqlConnection connection, string spName, params object[] parameterValues)
        {
            if( connection == null ) throw new ArgumentNullException( "connection" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                // 比缓存中加载存储过程参数
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connection, spName);
                // 给存储过程参数分配值
                AssignParameterValues(commandParameters, parameterValues);
                return ExecuteDataset(connection, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                return ExecuteDataset(connection, CommandType.StoredProcedure, spName);
            }
        }
        
        /// <summary>
        /// 执行指定事务的命令,返回DataSet.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  DataSet ds = ExecuteDataset(trans, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param>事务</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名或T-SQL语句</param>
        /// <returns>返回一个包含结果集的DataSet</returns>
        public static DataSet ExecuteDataset(SqlTransaction transaction, CommandType commandType, string commandText)
        {
            return ExecuteDataset(transaction, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// 执行指定事务的命令,指定参数,返回DataSet.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  DataSet ds = ExecuteDataset(trans, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>事务</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名或T-SQL语句</param>
        /// <param>SqlParamter参数数组</param>
        /// <returns>返回一个包含结果集的DataSet</returns>
        public static DataSet ExecuteDataset(SqlTransaction transaction, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if( transaction == null ) throw new ArgumentNullException( "transaction" );
            if( transaction != null && transaction.Connection == null ) throw new ArgumentException( "The transaction was rollbacked or commited, please provide an open transaction.", "transaction" );
            // 预处理
            SqlCommand cmd = new SqlCommand();
            bool mustCloseConnection = false;
            PrepareCommand(cmd, transaction.Connection, transaction, commandType, commandText, commandParameters, out mustCloseConnection );
                
            // 创建 DataAdapter & DataSet
            using( SqlDataAdapter da = new SqlDataAdapter(cmd) )
            {
                DataSet ds = new DataSet();
                da.Fill(ds);
                cmd.Parameters.Clear();
                return ds;
            }    
        }
        
        /// <summary>
        /// 执行指定事务的命令,指定参数值,返回DataSet.
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输入参数和返回值.
        /// 示例.:  
        ///  DataSet ds = ExecuteDataset(trans, "GetOrders", 24, 36);
        /// </remarks>
        /// <param>事务</param>
        /// <param>存储过程名</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回一个包含结果集的DataSet</returns>
        public static DataSet ExecuteDataset(SqlTransaction transaction, string spName, params object[] parameterValues)
        {
            if( transaction == null ) throw new ArgumentNullException( "transaction" );
            if( transaction != null && transaction.Connection == null ) throw new ArgumentException( "The transaction was rollbacked or commited, please provide an open transaction.", "transaction" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                // 从缓存中加载存储过程参数
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(transaction.Connection, spName);
                // 给存储过程参数分配值
                AssignParameterValues(commandParameters, parameterValues);
                return ExecuteDataset(transaction, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                return ExecuteDataset(transaction, CommandType.StoredProcedure, spName);
            }
        }
        #endregion ExecuteDataset数据集命令结束
        
        #region ExecuteReader 数据阅读器
        /// <summary>
        /// 枚举,标识数据库连接是由SqlHelper提供还是由调用者提供
        /// </summary>
        private enum SqlConnectionOwnership    
        {
            /// <summary>由SqlHelper提供连接</summary>
            Internal, 
            /// <summary>由调用者提供连接</summary>
            External
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的数据阅读器.
        /// </summary>
        /// <remarks>
        /// 如果是SqlHelper打开连接,当连接关闭DataReader也将关闭.
        /// 如果是调用都打开连接,DataReader由调用都管理.
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>一个有效的事务,或者为 ‘null‘</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名或T-SQL语句</param>
        /// <param>SqlParameters参数数组,如果没有参数则为‘null‘</param>
        /// <param>标识数据库连接对象是由调用者提供还是由SqlHelper提供</param>
        /// <returns>返回包含结果集的SqlDataReader</returns>
        private static SqlDataReader ExecuteReader(SqlConnection connection, SqlTransaction transaction, CommandType commandType, string commandText, SqlParameter[] commandParameters, SqlConnectionOwnership connectionOwnership)
        {    
            if( connection == null ) throw new ArgumentNullException( "connection" );
            bool mustCloseConnection = false;
            // 创建命令
            SqlCommand cmd = new SqlCommand();
            try
            {
                PrepareCommand(cmd, connection, transaction, commandType, commandText, commandParameters, out mustCloseConnection );
            
                // 创建数据阅读器
                SqlDataReader dataReader;
                if (connectionOwnership == SqlConnectionOwnership.External)
                {
                    dataReader = cmd.ExecuteReader();
                }
                else
                {
                    dataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                }
            
                // 清除参数,以便再次使用..
                // HACK: There is a problem here, the output parameter values are fletched 
                // when the reader is closed, so if the parameters are detached from the command
                // then the SqlReader can磘 set its values. 
                // When this happen, the parameters can磘 be used again in other command.
                bool canClear = true;
                foreach(SqlParameter commandParameter in cmd.Parameters)
                {
                    if (commandParameter.Direction != ParameterDirection.Input)
                        canClear = false;
                }
            
                if (canClear)
                {
                    cmd.Parameters.Clear();
                }
                return dataReader;
            }
            catch
            {
                if( mustCloseConnection )
                    connection.Close();
                throw;
            }
        }
        
        /// <summary>
        /// 执行指定数据库连接字符串的数据阅读器.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  SqlDataReader dr = ExecuteReader(connString, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param>一个有效的数据库连接字符串</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名或T-SQL语句</param>
        /// <returns>返回包含结果集的SqlDataReader</returns>
        public static SqlDataReader ExecuteReader(string connectionString, CommandType commandType, string commandText)
        {
            return ExecuteReader(connectionString, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// 执行指定数据库连接字符串的数据阅读器,指定参数.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  SqlDataReader dr = ExecuteReader(connString, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的数据库连接字符串</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名或T-SQL语句</param>
        /// <param>SqlParamter参数数组(new SqlParameter("@prodid", 24))</param>
        /// <returns>返回包含结果集的SqlDataReader</returns>
        public static SqlDataReader ExecuteReader(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if( connectionString == null || connectionString.Length == 0 ) throw new ArgumentNullException( "connectionString" );
            SqlConnection connection = null;
            try
            {
                connection = new SqlConnection(connectionString);
                connection.Open();
                return ExecuteReader(connection, null, commandType, commandText, commandParameters,SqlConnectionOwnership.Internal);
            }
            catch
            {
                // If we fail to return the SqlDatReader, we need to close the connection ourselves
                if( connection != null ) connection.Close();
                throw;
            }
            
        }
        
        /// <summary>
        /// 执行指定数据库连接字符串的数据阅读器,指定参数值.
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输出参数和返回值参数.
        /// 示例:  
        ///  SqlDataReader dr = ExecuteReader(connString, "GetOrders", 24, 36);
        /// </remarks>
        /// <param>一个有效的数据库连接字符串</param>
        /// <param>存储过程名</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回包含结果集的SqlDataReader</returns>
        public static SqlDataReader ExecuteReader(string connectionString, string spName, params object[] parameterValues)
        {
            if( connectionString == null || connectionString.Length == 0 ) throw new ArgumentNullException( "connectionString" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);
                AssignParameterValues(commandParameters, parameterValues);
                return ExecuteReader(connectionString, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                return ExecuteReader(connectionString, CommandType.StoredProcedure, spName);
            }
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的数据阅读器.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  SqlDataReader dr = ExecuteReader(conn, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名或T-SQL语句</param>
        /// <returns>返回包含结果集的SqlDataReader</returns>
        public static SqlDataReader ExecuteReader(SqlConnection connection, CommandType commandType, string commandText)
        {
            return ExecuteReader(connection, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// [调用者方式]执行指定数据库连接对象的数据阅读器,指定参数.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  SqlDataReader dr = ExecuteReader(conn, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>SqlParamter参数数组</param>
        /// <returns>返回包含结果集的SqlDataReader</returns>
        public static SqlDataReader ExecuteReader(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            return ExecuteReader(connection, (SqlTransaction)null, commandType, commandText, commandParameters, SqlConnectionOwnership.External);
        }
        
        /// <summary>
        /// [调用者方式]执行指定数据库连接对象的数据阅读器,指定参数值.
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输出参数和返回值参数.
        /// 示例:  
        ///  SqlDataReader dr = ExecuteReader(conn, "GetOrders", 24, 36);
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>T存储过程名</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回包含结果集的SqlDataReader</returns>
        public static SqlDataReader ExecuteReader(SqlConnection connection, string spName, params object[] parameterValues)
        {
            if( connection == null ) throw new ArgumentNullException( "connection" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connection, spName);
                AssignParameterValues(commandParameters, parameterValues);
                return ExecuteReader(connection, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                return ExecuteReader(connection, CommandType.StoredProcedure, spName);
            }
        }
        
        /// <summary>
        /// [调用者方式]执行指定数据库事务的数据阅读器,指定参数值.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  SqlDataReader dr = ExecuteReader(trans, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param>一个有效的连接事务</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <returns>返回包含结果集的SqlDataReader</returns>
        public static SqlDataReader ExecuteReader(SqlTransaction transaction, CommandType commandType, string commandText)
        {
            return ExecuteReader(transaction, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// [调用者方式]执行指定数据库事务的数据阅读器,指定参数.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///   SqlDataReader dr = ExecuteReader(trans, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的连接事务</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <param>分配给命令的SqlParamter参数数组</param>
        /// <returns>返回包含结果集的SqlDataReader</returns>
        public static SqlDataReader ExecuteReader(SqlTransaction transaction, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if( transaction == null ) throw new ArgumentNullException( "transaction" );
            if( transaction != null && transaction.Connection == null ) throw new ArgumentException( "The transaction was rollbacked or commited, please provide an open transaction.", "transaction" );
            return ExecuteReader(transaction.Connection, transaction, commandType, commandText, commandParameters, SqlConnectionOwnership.External);
        }
        
        /// <summary>
        /// [调用者方式]执行指定数据库事务的数据阅读器,指定参数值.
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输出参数和返回值参数.
        /// 
        /// 示例:  
        ///  SqlDataReader dr = ExecuteReader(trans, "GetOrders", 24, 36);
        /// </remarks>
        /// <param>一个有效的连接事务</param>
        /// <param>存储过程名称</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回包含结果集的SqlDataReader</returns>
        public static SqlDataReader ExecuteReader(SqlTransaction transaction, string spName, params object[] parameterValues)
        {
            if( transaction == null ) throw new ArgumentNullException( "transaction" );
            if( transaction != null && transaction.Connection == null ) throw new ArgumentException( "The transaction was rollbacked or commited, please provide an open transaction.", "transaction" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            // 如果有参数值
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(transaction.Connection, spName);
                AssignParameterValues(commandParameters, parameterValues);
                return ExecuteReader(transaction, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                // 没有参数值
                return ExecuteReader(transaction, CommandType.StoredProcedure, spName);
            }
        }
        #endregion ExecuteReader数据阅读器
            
        #region ExecuteScalar 返回结果集中的第一行第一列        
        /// <summary>
        /// 执行指定数据库连接字符串的命令,返回结果集中的第一行第一列.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  int orderCount = (int)ExecuteScalar(connString, CommandType.StoredProcedure, "GetOrderCount");
        /// </remarks>
        /// <param>一个有效的数据库连接字符串</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <returns>返回结果集中的第一行第一列</returns>
        public static object ExecuteScalar(string connectionString, CommandType commandType, string commandText)
        {
            // 执行参数为空的方法
            return ExecuteScalar(connectionString, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// 执行指定数据库连接字符串的命令,指定参数,返回结果集中的第一行第一列.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  int orderCount = (int)ExecuteScalar(connString, CommandType.StoredProcedure, "GetOrderCount", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的数据库连接字符串</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <param>分配给命令的SqlParamter参数数组</param>
        /// <returns>返回结果集中的第一行第一列</returns>
        public static object ExecuteScalar(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if( connectionString == null || connectionString.Length == 0 ) throw new ArgumentNullException( "connectionString" );
            // 创建并打开数据库连接对象,操作完成释放对象.
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();
                // 调用指定数据库连接字符串重载方法.
                return ExecuteScalar(connection, commandType, commandText, commandParameters);
            }
        }
        
        /// <summary>
        /// 执行指定数据库连接字符串的命令,指定参数值,返回结果集中的第一行第一列.
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输出参数和返回值参数.
        /// 
        /// 示例:  
        ///  int orderCount = (int)ExecuteScalar(connString, "GetOrderCount", 24, 36);
        /// </remarks>
        /// <param>一个有效的数据库连接字符串</param>
        /// <param>存储过程名称</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回结果集中的第一行第一列</returns>
        public static object ExecuteScalar(string connectionString, string spName, params object[] parameterValues)
        {
            if( connectionString == null || connectionString.Length == 0 ) throw new ArgumentNullException( "connectionString" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            
            // 如果有参数值
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                // 从缓存中加载存储过程参数,如果缓存中不存在则从数据库中检索参数信息并加载到缓存中. ()
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);
                // 给存储过程参数赋值
                AssignParameterValues(commandParameters, parameterValues);
                // 调用重载方法
                return ExecuteScalar(connectionString, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                // 没有参数值
                return ExecuteScalar(connectionString, CommandType.StoredProcedure, spName);
            }
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的命令,返回结果集中的第一行第一列.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  int orderCount = (int)ExecuteScalar(conn, CommandType.StoredProcedure, "GetOrderCount");
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <returns>返回结果集中的第一行第一列</returns>
        public static object ExecuteScalar(SqlConnection connection, CommandType commandType, string commandText)
        {
            // 执行参数为空的方法
            return ExecuteScalar(connection, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的命令,指定参数,返回结果集中的第一行第一列.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  int orderCount = (int)ExecuteScalar(conn, CommandType.StoredProcedure, "GetOrderCount", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <param>分配给命令的SqlParamter参数数组</param>
        /// <returns>返回结果集中的第一行第一列</returns>
        public static object ExecuteScalar(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if( connection == null ) throw new ArgumentNullException( "connection" );
            // 创建SqlCommand命令,并进行预处理
            SqlCommand cmd = new SqlCommand();
            bool mustCloseConnection = false;
            PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters, out mustCloseConnection );
                
            // 执行SqlCommand命令,并返回结果.
            object retval = cmd.ExecuteScalar();
                
            // 清除参数,以便再次使用.
            cmd.Parameters.Clear();
            if( mustCloseConnection )
                connection.Close();
            return retval;
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的命令,指定参数值,返回结果集中的第一行第一列.
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输出参数和返回值参数.
        /// 
        /// 示例:  
        ///  int orderCount = (int)ExecuteScalar(conn, "GetOrderCount", 24, 36);
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>存储过程名称</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回结果集中的第一行第一列</returns>
        public static object ExecuteScalar(SqlConnection connection, string spName, params object[] parameterValues)
        {
            if( connection == null ) throw new ArgumentNullException( "connection" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            // 如果有参数值
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                // 从缓存中加载存储过程参数,如果缓存中不存在则从数据库中检索参数信息并加载到缓存中. ()
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connection, spName);
                // 给存储过程参数赋值
                AssignParameterValues(commandParameters, parameterValues);
                // 调用重载方法
                return ExecuteScalar(connection, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                // 没有参数值
                return ExecuteScalar(connection, CommandType.StoredProcedure, spName);
            }
        }
        
        /// <summary>
        /// 执行指定数据库事务的命令,返回结果集中的第一行第一列.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  int orderCount = (int)ExecuteScalar(trans, CommandType.StoredProcedure, "GetOrderCount");
        /// </remarks>
        /// <param>一个有效的连接事务</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <returns>返回结果集中的第一行第一列</returns>
        public static object ExecuteScalar(SqlTransaction transaction, CommandType commandType, string commandText)
        {
            // 执行参数为空的方法
            return ExecuteScalar(transaction, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// 执行指定数据库事务的命令,指定参数,返回结果集中的第一行第一列.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  int orderCount = (int)ExecuteScalar(trans, CommandType.StoredProcedure, "GetOrderCount", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的连接事务</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句</param>
        /// <param>分配给命令的SqlParamter参数数组</param>
        /// <returns>返回结果集中的第一行第一列</returns>
        public static object ExecuteScalar(SqlTransaction transaction, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if( transaction == null ) throw new ArgumentNullException( "transaction" );
            if( transaction != null && transaction.Connection == null ) throw new ArgumentException( "The transaction was rollbacked or commited, please provide an open transaction.", "transaction" );
            // 创建SqlCommand命令,并进行预处理
            SqlCommand cmd = new SqlCommand();
            bool mustCloseConnection = false;
            PrepareCommand(cmd, transaction.Connection, transaction, commandType, commandText, commandParameters, out mustCloseConnection );
                
            // 执行SqlCommand命令,并返回结果.
            object retval = cmd.ExecuteScalar();
                
            // 清除参数,以便再次使用.
            cmd.Parameters.Clear();
            return retval;
        }
        
        /// <summary>
        /// 执行指定数据库事务的命令,指定参数值,返回结果集中的第一行第一列.
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输出参数和返回值参数.
        /// 
        /// 示例:  
        ///  int orderCount = (int)ExecuteScalar(trans, "GetOrderCount", 24, 36);
        /// </remarks>
        /// <param>一个有效的连接事务</param>
        /// <param>存储过程名称</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回结果集中的第一行第一列</returns>
        public static object ExecuteScalar(SqlTransaction transaction, string spName, params object[] parameterValues)
        {
            if( transaction == null ) throw new ArgumentNullException( "transaction" );
            if( transaction != null && transaction.Connection == null ) throw new ArgumentException( "The transaction was rollbacked or commited, please provide an open transaction.", "transaction" );
            if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );
            // 如果有参数值
            if ((parameterValues != null) && (parameterValues.Length > 0)) 
            {
                // PPull the parameters for this stored procedure from the parameter cache ()
                SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(transaction.Connection, spName);
                // 给存储过程参数赋值
                AssignParameterValues(commandParameters, parameterValues);
                // 调用重载方法
                return ExecuteScalar(transaction, CommandType.StoredProcedure, spName, commandParameters);
            }
            else 
            {
                // 没有参数值
                return ExecuteScalar(transaction, CommandType.StoredProcedure, spName);
            }
        }
        #endregion ExecuteScalar 
               
        #region ExecuteXmlReader XML阅读器
        /// <summary>
        /// 执行指定数据库连接对象的SqlCommand命令,并产生一个XmlReader对象做为结果集返回.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  XmlReader r = ExecuteXmlReader(conn, CommandType.StoredProcedure, "GetOrders");
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句 using "FOR XML AUTO"</param>
        /// <returns>返回XmlReader结果集对象.</returns>
        public static XmlReader ExecuteXmlReader(SqlConnection connection, CommandType commandType, string commandText)
        {
            // 执行参数为空的方法
            return ExecuteXmlReader(connection, commandType, commandText, (SqlParameter[])null);
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的SqlCommand命令,并产生一个XmlReader对象做为结果集返回,指定参数.
        /// </summary>
        /// <remarks>
        /// 示例:  
        ///  XmlReader r = ExecuteXmlReader(conn, CommandType.StoredProcedure, "GetOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>命令类型 (存储过程,命令文本或其它)</param>
        /// <param>存储过程名称或T-SQL语句 using "FOR XML AUTO"</param>
        /// <param>分配给命令的SqlParamter参数数组</param>
        /// <returns>返回XmlReader结果集对象.</returns>
        public static XmlReader ExecuteXmlReader(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if( connection == null ) throw new ArgumentNullException( "connection" );
            bool mustCloseConnection = false;
            // 创建SqlCommand命令,并进行预处理
            SqlCommand cmd = new SqlCommand();
            try
            {
                PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters, out mustCloseConnection );
            
                // 执行命令
                XmlReader retval = cmd.ExecuteXmlReader();
            
                // 清除参数,以便再次使用.
                cmd.Parameters.Clear();
                return retval;
            }
            catch
            {    
                if( mustCloseConnection )
                    connection.Close();
                throw;
            }
        }
        
        /// <summary>
        /// 执行指定数据库连接对象的SqlCommand命令,并产生一个XmlReader对象做为结果集返回,指定参数值.
        /// </summary>
        /// <remarks>
        /// 此方法不提供访问存储过程输出参数和返回值参数.
        /// 
        /// 示例:  
        ///  XmlReader r = ExecuteXmlReader(conn, "GetOrders", 24, 36);
        /// </remarks>
        /// <param>一个有效的数据库连接对象</param>
        /// <param>存储过程名称 using "FOR XML AUTO"</param>
        /// <param>分配给存储过程输入参数的对象数组</param>
        /// <returns>返回XmlReader结果集对象.</returns>
        public static XmlReader ExecuteXmlReader(SqlConnection connection, string spName, params object[] parame