C# 操作SQL通用类SQLHelper

SqlHelper（一）

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

/// <summary>
/// 数据库的通用访问代码
/// 此类为抽象类，不允许实例化，在应用时直接调用即可
/// </summary>
public abstract class SqlHelper
{
    //获取数据库连接字符串，其属于静态变量且只读，项目中所有文档可以直接使用，但不能修改
    public static readonly string ConnectionStringLocalTransaction = ConfigurationManager.ConnectionStrings["pubsConnectionString"].ConnectionString;

    // 哈希表用来存储缓存的参数信息，哈希表可以存储任意类型的参数。
    private static Hashtable parmCache = Hashtable.Synchronized(new Hashtable());

    /// <summary>
    ///执行一个不需要返回值的SqlCommand命令，通过指定专用的连接字符串。
    /// 使用参数数组形式提供参数列表 
    /// </summary>
    /// <remarks>
    /// 使用示例：
    ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="connectionString">一个有效的数据库连接字符串</param>
    /// <param name="commandType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
    /// <param name="commandText">存储过程的名字或者 T-SQL 语句</param>
    /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
    /// <returns>返回一个数值表示此SqlCommand命令执行后影响的行数</returns>
    public static int ExecuteNonQuery(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
    {
        SqlCommand cmd = new SqlCommand();
        using (SqlConnection conn = new SqlConnection(connectionString))
        {
            //通过PrePareCommand方法将参数逐个加入到SqlCommand的参数集合中
            PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
            int val = cmd.ExecuteNonQuery();
            //清空SqlCommand中的参数列表
            cmd.Parameters.Clear();
            return val;
        }
    }

    /// <summary>
    ///执行一条不返回结果的SqlCommand，通过一个已经存在的数据库连接 
    /// 使用参数数组提供参数
    /// </summary>
    /// <remarks>
    /// 使用示例：  
    ///  int result = ExecuteNonQuery(conn, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="conn">一个现有的数据库连接</param>
    /// <param name="commandType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
    /// <param name="commandText">存储过程的名字或者 T-SQL 语句</param>
    /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
    /// <returns>返回一个数值表示此SqlCommand命令执行后影响的行数</returns>
    public static int ExecuteNonQuery(SqlConnection connection, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
    {
        SqlCommand cmd = new SqlCommand();
        PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
        int val = cmd.ExecuteNonQuery();
        cmd.Parameters.Clear();
        return val;
    }

    /// <summary>
    /// 执行一条不返回结果的SqlCommand，通过一个已经存在的数据库事务处理 
    /// 使用参数数组提供参数
    /// </summary>
    /// <remarks>
    /// 使用示例： 
    ///  int result = ExecuteNonQuery(trans, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="trans">一个存在的 sql 事务处理</param>
    /// <param name="commandType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
    /// <param name="commandText">存储过程的名字或者 T-SQL 语句</param>
    /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
    /// <returns>返回一个数值表示此SqlCommand命令执行后影响的行数</returns>
    public static int ExecuteNonQuery(SqlTransaction trans, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
    {
        SqlCommand cmd = new SqlCommand();
        PrepareCommand(cmd, trans.Connection, trans, cmdType, cmdText, commandParameters);
        int val = cmd.ExecuteNonQuery();
        cmd.Parameters.Clear();
        return val;
    }

    /// <summary>
    /// 执行一条返回结果集的SqlCommand命令，通过专用的连接字符串。
    /// 使用参数数组提供参数
    /// </summary>
    /// <remarks>
    /// 使用示例：  
    ///  SqlDataReader r = ExecuteReader(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="connectionString">一个有效的数据库连接字符串</param>
    /// <param name="commandType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
    /// <param name="commandText">存储过程的名字或者 T-SQL 语句</param>
    /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
    /// <returns>返回一个包含结果的SqlDataReader</returns>
    public static SqlDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
    {
        SqlCommand cmd = new SqlCommand();
        SqlConnection conn = new SqlConnection(connectionString);

        // 在这里使用try/catch处理是因为如果方法出现异常，则SqlDataReader就不存在，
        //CommandBehavior.CloseConnection的语句就不会执行，触发的异常由catch捕获。
        //关闭数据库连接，并通过throw再次引发捕捉到的异常。
        try
        {
            PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
            SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
            cmd.Parameters.Clear();
            return rdr;
        }
        catch
        {
            conn.Close();
            throw;
        }
    }

    /// <summary>
    /// 执行一条返回第一条记录第一列的SqlCommand命令，通过专用的连接字符串。 
    /// 使用参数数组提供参数
    /// </summary>
    /// <remarks>
    /// 使用示例：  
    ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="connectionString">一个有效的数据库连接字符串</param>
    /// <param name="commandType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
    /// <param name="commandText">存储过程的名字或者 T-SQL 语句</param>
    /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
    /// <returns>返回一个object类型的数据，可以通过 Convert.To{Type}方法转换类型</returns>
    public static object ExecuteScalar(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
    {
        SqlCommand cmd = new SqlCommand();
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
            object val = cmd.ExecuteScalar();
            cmd.Parameters.Clear();
            return val;
        }
    }

    /// <summary>
    /// 执行一条返回第一条记录第一列的SqlCommand命令，通过已经存在的数据库连接。
    /// 使用参数数组提供参数
    /// </summary>
    /// <remarks>
    /// 使用示例： 
    ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="conn">一个已经存在的数据库连接</param>
    /// <param name="commandType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
    /// <param name="commandText">存储过程的名字或者 T-SQL 语句</param>
    /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
    /// <returns>返回一个object类型的数据，可以通过 Convert.To{Type}方法转换类型</returns>
    public static object ExecuteScalar(SqlConnection connection, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
    {
        SqlCommand cmd = new SqlCommand();
        PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
        object val = cmd.ExecuteScalar();
        cmd.Parameters.Clear();
        return val;
    }

    /// <summary>
    /// 缓存参数数组
    /// </summary>
    /// <param name="cacheKey">参数缓存的键值</param>
    /// <param name="cmdParms">被缓存的参数列表</param>
    public static void CacheParameters(string cacheKey, params SqlParameter[] commandParameters)
    {
        parmCache[cacheKey] = commandParameters;
    }

    /// <summary>
    /// 获取被缓存的参数
    /// </summary>
    /// <param name="cacheKey">用于查找参数的KEY值</param>
    /// <returns>返回缓存的参数数组</returns>
    public static SqlParameter[] GetCachedParameters(string cacheKey)
    {
        SqlParameter[] cachedParms = (SqlParameter[])parmCache[cacheKey];
        if (cachedParms == null)
            return null;
        //新建一个参数的克隆列表
        SqlParameter[] clonedParms = new SqlParameter[cachedParms.Length];
        //通过循环为克隆参数列表赋值
        for (int i = 0, j = cachedParms.Length; i < j; i++)
            //使用clone方法复制参数列表中的参数
            clonedParms[i] = (SqlParameter)((ICloneable)cachedParms[i]).Clone();
        return clonedParms;
    }

    /// <summary>
    /// 为执行命令准备参数
    /// </summary>
    /// <param name="cmd">SqlCommand 命令</param>
    /// <param name="conn">已经存在的数据库连接</param>
    /// <param name="trans">数据库事务处理</param>
    /// <param name="cmdType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
    /// <param name="cmdText">Command text，T-SQL语句 例如 Select * from Products</param>
    /// <param name="cmdParms">返回带参数的命令</param>
    private static void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, CommandType cmdType, string cmdText, SqlParameter[] cmdParms)
    {
        //判断数据库连接状态
        if (conn.State != ConnectionState.Open)
            conn.Open();
        cmd.Connection = conn;
        cmd.CommandText = cmdText;
        //判断是否需要事务处理
        if (trans != null)
            cmd.Transaction = trans;
        cmd.CommandType = cmdType;
        if (cmdParms != null)
        {
            cmd.Parameters.AddRange(cmdParms);
        }
    }
}

SqlHelper（二）

using System;
using System.Data;
using System.Data.SqlClient;
using System.Collections;
namespace DotNet.Utilities
{
    /// <summary>
    /// 数据库的通用访问代码
    /// 此类为抽象类，不允许实例化，在应用时直接调用即可
    /// </summary>
    public abstract class SqlHelper
    {
        /// <summary>
        /// 数据库连接字符串
        /// </summary>
        public static readonly string connectionString = System.Configuration.ConfigurationSettings.AppSettings["con"].ToString().Trim();

        // Hashtable to store cached parameters
        private static Hashtable _parmCache = Hashtable.Synchronized(new Hashtable());

        #region ExecteNonQuery方法
        /// <summary>
        /// 执行一个不需要返回值的SqlCommand命令，通过指定专用的连接字符串。
        /// 使用参数数组形式提供参数列表 
        /// </summary>
        /// <param name="connectionString">一个有效的数据库连接字符串</param>
        /// <param name="cmdType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
        /// <param name="cmdText">存储过程的名字或者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>返回一个数值表示此SqlCommand命令执行后影响的行数</returns>
        public static int ExecteNonQuery(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                //通过PrePareCommand方法将参数逐个加入到SqlCommand的参数集合中
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                int val = cmd.ExecuteNonQuery();
                //清空SqlCommand中的参数列表
                cmd.Parameters.Clear();
                return val;
            }
        }

        /// <summary>
        ///执行一个不需要返回值的SqlCommand命令，通过指定专用的连接字符串。
        /// 使用参数数组形式提供参数列表 
        /// </summary>
        /// <param name="cmdType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
        /// <param name="cmdText">存储过程的名字或者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>返回一个数值表示此SqlCommand命令执行后影响的行数</returns>
        public static int ExecteNonQuery(CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecteNonQuery(connectionString, cmdType, cmdText, commandParameters);
        }

        /// <summary>
        ///存储过程专用
        /// </summary>
        /// <param name="cmdText">存储过程的名字</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>返回一个数值表示此SqlCommand命令执行后影响的行数</returns>
        public static int ExecteNonQueryProducts(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecteNonQuery(CommandType.StoredProcedure, cmdText, commandParameters);
        }

        /// <summary>
        ///Sql语句专用
        /// </summary>
        /// <param name="cmdText">T_Sql语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>返回一个数值表示此SqlCommand命令执行后影响的行数</returns>
        public static int ExecteNonQueryText(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecteNonQuery(CommandType.Text, cmdText, commandParameters);
        }

        #endregion

        #region GetTable方法

        /// <summary>
        /// 执行一条返回结果集的SqlCommand，通过一个已经存在的数据库连接
        /// 使用参数数组提供参数
        /// </summary>
        /// <param name="connecttionString">一个现有的数据库连接</param>
        /// <param name="cmdTye">SqlCommand命令类型</param>
        /// <param name="cmdText">存储过程的名字或者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>返回一个表集合(DataTableCollection)表示查询得到的数据集</returns>
        public static DataTableCollection GetTable(string connecttionString, CommandType cmdTye, string cmdText, SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            DataSet ds = new DataSet();
            using (SqlConnection conn = new SqlConnection(connecttionString))
            {
                PrepareCommand(cmd, conn, null, cmdTye, cmdText, commandParameters);
                SqlDataAdapter adapter = new SqlDataAdapter();
                adapter.SelectCommand = cmd;
                adapter.Fill(ds);
            }
            return ds.Tables;
        }

        /// <summary>
        /// 执行一条返回结果集的SqlCommand，通过一个已经存在的数据库连接
        /// 使用参数数组提供参数
        /// </summary>
        /// <param name="cmdTye">SqlCommand命令类型</param>
        /// <param name="cmdText">存储过程的名字或者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>返回一个表集合(DataTableCollection)表示查询得到的数据集</returns>
        public static DataTableCollection GetTable(CommandType cmdTye, string cmdText, SqlParameter[] commandParameters)
        {
            return GetTable(connectionString, cmdTye, cmdText, commandParameters);
        }

        /// <summary>
        /// 存储过程专用
        /// </summary>
        /// <param name="cmdText">存储过程的名字或者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>返回一个表集合(DataTableCollection)表示查询得到的数据集</returns>
        public static DataTableCollection GetTableProducts(string cmdText, SqlParameter[] commandParameters)
        {
            return GetTable(CommandType.StoredProcedure, cmdText, commandParameters);
        }

        /// <summary>
        /// Sql语句专用
        /// </summary>
        /// <param name="cmdText"> T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>返回一个表集合(DataTableCollection)表示查询得到的数据集</returns>
        public static DataTableCollection GetTableText(string cmdText, SqlParameter[] commandParameters)
        {
            return GetTable(CommandType.Text, cmdText, commandParameters);
        }

        #endregion

        /// <summary>
        /// 为执行命令准备参数
        /// </summary>
        /// <param name="cmd">SqlCommand 命令</param>
        /// <param name="conn">已经存在的数据库连接</param>
        /// <param name="trans">数据库事物处理</param>
        /// <param name="cmdType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
        /// <param name="cmdText">Command text，T-SQL语句 例如 Select * from Products</param>
        /// <param name="cmdParms">返回带参数的命令</param>
        private static void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, CommandType cmdType, string cmdText, SqlParameter[] cmdParms)
        {
            //判断数据库连接状态
            if (conn.State != ConnectionState.Open)
                conn.Open();
            cmd.Connection = conn;
            cmd.CommandText = cmdText;
            //判断是否需要事物处理
            if (trans != null)
                cmd.Transaction = trans;
            cmd.CommandType = cmdType;
            if (cmdParms != null)
            {
                cmd.Parameters.AddRange(cmdParms);
            }
        }

        /// <summary>
        /// Execute a SqlCommand that returns a resultset against the database specified in the connection string 
        /// using the provided parameters.
        /// </summary>
        /// <param name="connectionString">一个有效的数据库连接字符串</param>
        /// <param name="cmdType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
        /// <param name="cmdText">存储过程的名字或者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>A SqlDataReader containing the results</returns>
        public static SqlDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            SqlConnection conn = new SqlConnection(connectionString);
            // we use a try/catch here because if the method throws an exception we want to 
            // close the connection throw code, because no datareader will exist, hence the 
            // commandBehaviour.CloseConnection will not work
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                cmd.Parameters.Clear();
                return rdr;
            }
            catch
            {
                conn.Close();
                throw;
            }
        }

        #region ExecuteDataSet方法

        /// <summary>
        /// return a dataset
        /// </summary>
        /// <param name="connectionString">一个有效的数据库连接字符串</param>
        /// <param name="cmdType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
        /// <param name="cmdText">存储过程的名字或者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>return a dataset</returns>
        public static DataSet ExecuteDataSet(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            try
            {
                using (SqlConnection conn = new SqlConnection(connectionString))
                {
                    PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                    SqlDataAdapter da = new SqlDataAdapter();
                    DataSet ds = new DataSet();
                    da.SelectCommand = cmd;
                    da.Fill(ds);
                    return ds;
                }
            }
            catch
            {
                throw;
            }
        }

        /// <summary>
        /// 返回一个DataSet
        /// </summary>
        /// <param name="cmdType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
        /// <param name="cmdText">存储过程的名字或者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>return a dataset</returns>
        public static DataSet ExecuteDataSet(CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteDataSet(connectionString, cmdType, cmdText, commandParameters);
        }

        /// <summary>
        /// 返回一个DataSet
        /// </summary>
        /// <param name="cmdText">存储过程的名字</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>return a dataset</returns>
        public static DataSet ExecuteDataSetProducts(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteDataSet(connectionString, CommandType.StoredProcedure, cmdText, commandParameters);
        }

        /// <summary>
        /// 返回一个DataSet
        /// </summary>
        /// <param name="cmdText">T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>return a dataset</returns>
        public static DataSet ExecuteDataSetText(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteDataSet(connectionString, CommandType.Text, cmdText, commandParameters);
        }

        public static DataView ExecuteDataSet(string connectionString, string sortExpression, string direction, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            try
            {
                using (SqlConnection conn = new SqlConnection(connectionString))
                {
                    PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                    SqlDataAdapter da = new SqlDataAdapter();
                    DataSet ds = new DataSet();
                    da.SelectCommand = cmd;
                    da.Fill(ds);
                    DataView dv = ds.Tables[0].DefaultView;
                    dv.Sort = sortExpression + " " + direction;
                    return dv;
                }
            }
            catch
            {
                throw;
            }
        }
        #endregion

        #region // ExecuteScalar方法

        /// <summary>
        /// 返回第一行的第一列
        /// </summary>
        /// <param name="cmdType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
        /// <param name="cmdText">存储过程的名字或者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>返回一个对象</returns>
        public static object ExecuteScalar(CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteScalar(SqlHelper.connectionString, cmdType, cmdText, commandParameters);
        }

        /// <summary>
        /// 返回第一行的第一列存储过程专用
        /// </summary>
        /// <param name="cmdText">存储过程的名字</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>返回一个对象</returns>
        public static object ExecuteScalarProducts(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteScalar(SqlHelper.connectionString, CommandType.StoredProcedure, cmdText, commandParameters);
        }

        /// <summary>
        /// 返回第一行的第一列Sql语句专用
        /// </summary>
        /// <param name="cmdText">者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>返回一个对象</returns>
        public static object ExecuteScalarText(string cmdText, params SqlParameter[] commandParameters)
        {
            return ExecuteScalar(SqlHelper.connectionString, CommandType.Text, cmdText, commandParameters);
        }

        /// <summary>
        /// Execute a SqlCommand that returns the first column of the first record against the database specified in the connection string 
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">一个有效的数据库连接字符串</param>
        /// <param name="cmdType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
        /// <param name="cmdText">存储过程的名字或者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>An object that should be converted to the expected type using Convert.To{Type}</returns>
        public static object ExecuteScalar(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();

            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
                object val = cmd.ExecuteScalar();
                cmd.Parameters.Clear();
                return val;
            }
        }

        /// <summary>
        /// Execute a SqlCommand that returns the first column of the first record against an existing database connection 
        /// using the provided parameters.
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">一个有效的数据库连接字符串</param>
        /// <param name="cmdType">SqlCommand命令类型 (存储过程， T-SQL语句， 等等。)</param>
        /// <param name="cmdText">存储过程的名字或者 T-SQL 语句</param>
        /// <param name="commandParameters">以数组形式提供SqlCommand命令中用到的参数列表</param>
        /// <returns>An object that should be converted to the expected type using Convert.To{Type}</returns>
        public static object ExecuteScalar(SqlConnection connection, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
            object val = cmd.ExecuteScalar();
            cmd.Parameters.Clear();
            return val;
        }

        #endregion

        /// <summary>
        /// add parameter array to the cache
        /// </summary>
        /// <param name="cacheKey">Key to the parameter cache</param>
        /// <param name="cmdParms">an array of SqlParamters to be cached</param>
        public static void CacheParameters(string cacheKey, params SqlParameter[] commandParameters)
        {
            _parmCache[cacheKey] = commandParameters;
        }

        /// <summary>
        /// Retrieve cached parameters
        /// </summary>
        /// <param name="cacheKey">key used to lookup parameters</param>
        /// <returns>Cached SqlParamters array</returns>
        public static SqlParameter[] GetCachedParameters(string cacheKey)
        {
            SqlParameter[] cachedParms = (SqlParameter[])_parmCache[cacheKey];
            if (cachedParms == null)
                return null;
            SqlParameter[] clonedParms = new SqlParameter[cachedParms.Length];
            cachedParms.CopyTo(clonedParms, 0);
            return clonedParms;
        }

        /// <summary>
        /// 检查是否存在
        /// </summary>
        /// <param name="strSql">Sql语句</param>
        /// <param name="cmdParms">参数</param>
        /// <returns>bool结果</returns>
        public static bool Exists(string strSql, params SqlParameter[] cmdParms)
        {
            int cmdresult = Convert.ToInt32(ExecuteScalar(connectionString, CommandType.Text, strSql, cmdParms));
            return cmdresult != 0;
        }
    }
}

SqlHelper（三）

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Web.Configuration;

namespace DotNet
{
    public class SQLHelper
    {
        // 超时时间
        private static int Timeout = 1000;
        // 数据库名称
        public const String BestNet = "BestNet";
        // 存储过程名称
        public const String UserInfoCURD = "UserInfoCURD";
        // 数据库连接字符串
        private static Dictionary<String, String> ConnStrs = new Dictionary<String, String>();

        /// <summary>
        /// SQLServer操作类(静态构造函数)
        /// </summary>
        static SQLHelper()
        {
            ConnectionStringSettingsCollection configs = WebConfigurationManager.ConnectionStrings;
            foreach (ConnectionStringSettings config in configs)
            {
                ConnStrs.Add(config.Name, config.ConnectionString);
            }
        }

        /// <summary>
        /// 获取数据库连接
        /// </summary>
        /// <param name="database">数据库(配置文件内connectionStrings的name)</param>
        /// <returns>数据库连接</returns>
        private static SqlConnection GetConnection(string database)
        {
            if (string.IsNullOrEmpty(database))
            {
                throw new Exception("未设置参数：database");
            }
            if (!ConnStrs.ContainsKey(database))
            {
                throw new Exception("未找到数据库：" + database);
            }
            return new SqlConnection(ConnStrs[database]);
        }

        /// <summary>
        /// 获取SqlCommand
        /// </summary>
        /// <param name="conn">SqlConnection</param>
        /// <param name="transaction">SqlTransaction</param>
        /// <param name="cmdType">CommandType</param>
        /// <param name="sql">SQL</param>
        /// <param name="parms">SqlParameter数组</param>
        /// <returns></returns>
        private static SqlCommand GetCommand(SqlConnection conn, SqlTransaction transaction, CommandType cmdType, string sql, SqlParameter[] parms)
        {
            SqlCommand cmd = new SqlCommand(sql, conn);
            cmd.CommandType = cmdType;
            cmd.CommandTimeout = Timeout;
            if (transaction != null)
                cmd.Transaction = transaction;
            if (parms != null && parms.Length != 0)
                cmd.Parameters.AddRange(parms);
            return cmd;
        }

        /// <summary>
        /// 查询数据，返回DataTable
        /// </summary>
        /// <param name="database">数据库</param>
        /// <param name="sql">SQL语句或存储过程名</param>
        /// <param name="parms">参数</param>
        /// <param name="cmdType">查询类型(SQL语句/存储过程名)</param>
        /// <returns>DataTable</returns>
        public static DataTable QueryDataTable(string database, string sql, SqlParameter[] parms, CommandType cmdType)
        {
            if (string.IsNullOrEmpty(database))
            {
                throw new Exception("未设置参数：database");
            }
            if (string.IsNullOrEmpty(sql))
            {
                throw new Exception("未设置参数：sql");
            }

            try
            {
                using (SqlConnection conn = GetConnection(database))
                {
                    conn.Open();

                    using (SqlCommand cmd = GetCommand(conn, null, cmdType, sql, parms))
                    {
                        using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                        {
                            DataTable dt = new DataTable();
                            da.Fill(dt);
                            return dt;
                        }
                    }
                }
            }
            catch (SqlException ex)
            {
                System.Text.StringBuilder log = new System.Text.StringBuilder();
                log.Append("查询数据出错：");
                log.Append(ex);
                throw new Exception(log.ToString());
            }
        }

        /// <summary>
        /// 查询数据，返回DataSet
        /// </summary>
        /// <param name="database">数据库</param>
        /// <param name="sql">SQL语句或存储过程名</param>
        /// <param name="parms">参数</param>
        /// <param name="cmdType">查询类型(SQL语句/存储过程名)</param>
        /// <returns>DataSet</returns>
        public static DataSet QueryDataSet(string database, string sql, SqlParameter[] parms, CommandType cmdType)
        {
            if (string.IsNullOrEmpty(database))
            {
                throw new Exception("未设置参数：database");
            }
            if (string.IsNullOrEmpty(sql))
            {
                throw new Exception("未设置参数：sql");
            }

            try
            {
                using (SqlConnection conn = GetConnection(database))
                {
                    conn.Open();

                    using (SqlCommand cmd = GetCommand(conn, null, cmdType, sql, parms))
                    {
                        using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                        {
                            DataSet ds = new DataSet();
                            da.Fill(ds);
                            return ds;
                        }
                    }
                }
            }
            catch (SqlException ex)
            {
                System.Text.StringBuilder log = new System.Text.StringBuilder();
                log.Append("查询数据出错：");
                log.Append(ex);
                throw new Exception(log.ToString());
            }
        }

        /// <summary>
        /// 执行命令获取唯一值(第一行第一列)
        /// </summary>
        /// <param name="database">数据库</param>
        /// <param name="sql">SQL语句或存储过程名</param>
        /// <param name="parms">参数</param>
        /// <param name="cmdType">查询类型(SQL语句/存储过程名)</param>
        /// <returns>获取值</returns>
        public static object QueryScalar(string database, string sql, SqlParameter[] parms, CommandType cmdType)
        {
            if (string.IsNullOrEmpty(database))
            {
                throw new Exception("未设置参数：database");
            }
            if (string.IsNullOrEmpty(sql))
            {
                throw new Exception("未设置参数：sql");
            }
            try
            {
                using (SqlConnection conn = GetConnection(database))
                {
                    conn.Open();

                    using (SqlCommand cmd = GetCommand(conn, null, cmdType, sql, parms))
                    {
                        return cmd.ExecuteScalar();
                    }
                }
            }
            catch (SqlException ex)
            {
                System.Text.StringBuilder log = new System.Text.StringBuilder();
                log.Append("处理出错：");
                log.Append(ex);
                throw new Exception(log.ToString());
            }
        }

        /// <summary>
        /// 执行命令更新数据
        /// </summary>
        /// <param name="database">数据库</param>
        /// <param name="sql">SQL语句或存储过程名</param>
        /// <param name="parms">参数</param>
        /// <param name="cmdType">查询类型(SQL语句/存储过程名)</param>
        /// <returns>更新的行数</returns>
        public static int Execute(string database, string sql, SqlParameter[] parms, CommandType cmdType)
        {
            if (string.IsNullOrEmpty(database))
            {
                throw new Exception("未设置参数：database");
            }
            if (string.IsNullOrEmpty(sql))
            {
                throw new Exception("未设置参数：sql");
            }

            //返回(增删改)的更新行数
            int count = 0;

            try
            {
                using (SqlConnection conn = GetConnection(database))
                {
                    conn.Open();

                    using (SqlCommand cmd = GetCommand(conn, null, cmdType, sql, parms))
                    {
                        if (cmdType == CommandType.StoredProcedure)
                            cmd.Parameters.AddWithValue("@RETURN_VALUE", "").Direction = ParameterDirection.ReturnValue;

                        count = cmd.ExecuteNonQuery();

                        if (count <= 0)
                            if (cmdType == CommandType.StoredProcedure)
                                count = (int)cmd.Parameters["@RETURN_VALUE"].Value;
                    }
                }
            }
            catch (SqlException ex)
            {
                System.Text.StringBuilder log = new System.Text.StringBuilder();
                log.Append("处理出错：");
                log.Append(ex);
                throw new Exception(log.ToString());
            }
            return count;
        }

        /// <summary>
        /// 查询数据，返回DataTable
        /// </summary>
        /// <param name="database">数据库</param>
        /// <param name="sql">SQL语句或存储过程名</param>
        /// <param name="cmdType">查询类型(SQL语句/存储过程名)</param>
        /// <param name="values">参数</param>
        /// <returns>DataTable</returns>
        public static DataTable QueryDataTable(string database, string sql, CommandType cmdType, IDictionary<string, object> values)
        {
            SqlParameter[] parms = DicToParams(values);
            return QueryDataTable(database, sql, parms, cmdType);
        }

        /// <summary>
        /// 执行存储过程查询数据，返回DataSet
        /// </summary>
        /// <param name="database">数据库</param>
        /// <param name="sql">SQL语句或存储过程名</param>
        /// <param name="cmdType">查询类型(SQL语句/存储过程名)</param>
        /// <param name="values">参数
        /// <returns>DataSet</returns>
        public static DataSet QueryDataSet(string database, string sql, CommandType cmdType, IDictionary<string, object> values)
        {
            SqlParameter[] parms = DicToParams(values);
            return QueryDataSet(database, sql, parms, cmdType);
        }

        /// <summary>
        /// 执行命令获取唯一值(第一行第一列)
        /// </summary>
        /// <param name="database">数据库</param>
        /// <param name="sql">SQL语句或存储过程名</param>
        /// <param name="cmdType">查询类型(SQL语句/存储过程名)</param>
        /// <param name="values">参数</param>
        /// <returns>唯一值</returns>
        public static object QueryScalar(string database, string sql, CommandType cmdType, IDictionary<string, object> values)
        {
            SqlParameter[] parms = DicToParams(values);
            return QueryScalar(database, sql, parms, cmdType);
        }

        /// <summary>
        /// 执行命令更新数据
        /// </summary>
        /// <param name="database">数据库</param>
        /// <param name="sql">SQL语句或存储过程名</param>
        /// <param name="cmdType">查询类型(SQL语句/存储过程名)</param>
        /// <param name="values">参数</param>
        /// <returns>更新的行数</returns>
        public static int Execute(string database, string sql, CommandType cmdType, IDictionary<string, object> values)
        {
            SqlParameter[] parms = DicToParams(values);
            return Execute(database, sql, parms, cmdType);
        }

        /// <summary>
        /// 创建参数
        /// </summary>
        /// <param name="name">参数名</param>
        /// <param name="type">参数类型</param>
        /// <param name="size">参数大小</param>
        /// <param name="direction">参数方向(输入/输出)</param>
        /// <param name="value">参数值</param>
        /// <returns>新参数对象</returns>
        public static SqlParameter[] DicToParams(IDictionary<string, object> values)
        {
            if (values == null) return null;

            SqlParameter[] parms = new SqlParameter[values.Count];
            int index = 0;
            foreach (KeyValuePair<string, object> kv in values)
            {
                SqlParameter parm = null;
                if (kv.Value == null)
                {
                    parm = new SqlParameter(kv.Key, DBNull.Value);
                }
                else
                {
                    Type t = kv.Value.GetType();
                    parm = new SqlParameter(kv.Key, NetToSql(kv.Value.GetType()));
                    parm.Value = kv.Value;
                }
                parms[index++] = parm;
            }
            return parms;
        }


        /// <summary>
        /// .net类型转换为Sql类型
        /// </summary>
        /// <param name="t">.net类型</param>
        /// <returns>Sql类型</returns>
        public static SqlDbType NetToSql(Type t)
        {
            SqlDbType dbType = SqlDbType.Variant;
            switch (t.Name)
            {
                case "Int16":
                    dbType = SqlDbType.SmallInt;
                    break;
                case "Int32":
                    dbType = SqlDbType.Int;
                    break;
                case "Int64":
                    dbType = SqlDbType.BigInt;
                    break;
                case "Single":
                    dbType = SqlDbType.Real;
                    break;
                case "Decimal":
                    dbType = SqlDbType.Decimal;
                    break;
                case "Byte[]":
                    dbType = SqlDbType.VarBinary;
                    break;
                case "Boolean":
                    dbType = SqlDbType.Bit;
                    break;
                case "String":
                    dbType = SqlDbType.NVarChar;
                    break;
                case "Char[]":
                    dbType = SqlDbType.Char;
                    break;
                case "DateTime":
                    dbType = SqlDbType.DateTime;
                    break;
                case "DateTime2":
                    dbType = SqlDbType.DateTime2;
                    break;
                case "DateTimeOffset":
                    dbType = SqlDbType.DateTimeOffset;
                    break;
                case "TimeSpan":
                    dbType = SqlDbType.Time;
                    break;
                case "Guid":
                    dbType = SqlDbType.UniqueIdentifier;
                    break;
                case "Xml":
                    dbType = SqlDbType.Xml;
                    break;
                case "Object":
                    dbType = SqlDbType.Variant;
                    break;
            }
            return dbType;
        }
    }
}