C#访问MySQL数据库帮助类

MySQL数据库访问帮助类

1.项目添加引用官方MySQL动态库MySql.Data.dll

下载地址：MySql.Data.dll（也可以到官网下载动态库）项目添加引用

这里有一个Mysql帮助类的使用例子可以参考

C#简单三层结构设计UI、BLL、DAL

2.web.config配置数据库连接字符串

<?xml version="1.0"?>
<configuration>
  <appSettings>
    <!-- 连接字符串是否加密 -->
    <add key="ConStringEncrypt" value="false"/>
    <!-- 数据库连接字符串,（如果采用加密方式，上面一项要设置为true；加密工具，可在官方下载，
             如果使用明文这样server=127.0.0.1;database=.....,上面则设置为false。 -->
    <add key="ConnectionString" value="server=127.0.0.1;database=BenXHCMS;uid=sa;pwd=jyf"/>
  </appSettings>
</configuration>

3.数据库字符串读取类（多一个加密算法，可以自己添加）

    public class PubConstant
    {        
        /// <summary>
        /// 获取连接字符串
        /// </summary>
        public static string ConnectionString
        {           
            get 
            {
                string _connectionString = ConfigurationManager.AppSettings["ConnectionString"];       
                string ConStringEncrypt = ConfigurationManager.AppSettings["ConStringEncrypt"];
                if (ConStringEncrypt == "true")
                {
                    _connectionString = DESEncrypt.Decrypt(_connectionString);
                }
                return _connectionString; 
            }
        }

        /// <summary>
        /// 得到web.config里配置项的数据库连接字符串。
        /// </summary>
        /// <param name="configName"></param>
        /// <returns></returns>
        public static string GetConnectionString(string configName)
        {
            string connectionString = ConfigurationManager.AppSettings[configName];
            string ConStringEncrypt = ConfigurationManager.AppSettings["ConStringEncrypt"];
            if (ConStringEncrypt == "true")
            {
                connectionString = DESEncrypt.Decrypt(connectionString);
            }
            return connectionString;
        }


    }

4.MySQL数据库访问类--注意：对 MySql.Data.MySqlClient引用

using System;
using System.Collections;
using System.Collections.Specialized;
using System.Data;
using MySql.Data.MySqlClient;
using System.Configuration;
using System.Data.Common;
using System.Collections.Generic;
namespace Maticsoft.DBUtility
{
    /// <summary>
    /// 数据访问抽象基础类
    /// Copyright (C) Maticsoft
    /// </summary>
    public abstract class DbHelperMySQL
    {
        //数据库连接字符串(web.config来配置)，可以动态更改connectionString支持多数据库.        
        public static string connectionString = PubConstant.ConnectionString;
        public DbHelperMySQL()
        {            
        }

        #region 公用方法
        /// <summary>
        /// 得到最大值
        /// </summary>
        /// <param name="FieldName"></param>
        /// <param name="TableName"></param>
        /// <returns></returns>
        public static int GetMaxID(string FieldName, string TableName)
        {
            string strsql = "select max(" + FieldName + ")+1 from " + TableName;
            object obj = GetSingle(strsql);
            if (obj == null)
            {
                return 1;
            }
            else
            {
                return int.Parse(obj.ToString());
            }
        }
        /// <summary>
        /// 是否存在
        /// </summary>
        /// <param name="strSql"></param>
        /// <returns></returns>
        public static bool Exists(string strSql)
        {
            object obj = GetSingle(strSql);
            int cmdresult;
            if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
            {
                cmdresult = 0;
            }
            else
            {
                cmdresult = int.Parse(obj.ToString());
            }
            if (cmdresult == 0)
            {
                return false;
            }
            else
            {
                return true;
            }
        }    
        /// <summary>
        /// 是否存在（基于MySqlParameter）
        /// </summary>
        /// <param name="strSql"></param>
        /// <param name="cmdParms"></param>
        /// <returns></returns>
        public static bool Exists(string strSql, params MySqlParameter[] cmdParms)
        {
            object obj = GetSingle(strSql, cmdParms);
            int cmdresult;
            if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
            {
                cmdresult = 0;
            }
            else
            {
                cmdresult = int.Parse(obj.ToString());
            }
            if (cmdresult == 0)
            {
                return false;
            }
            else
            {
                return true;
            }
        }
        #endregion

        #region  执行简单SQL语句

        /// <summary>
        /// 执行SQL语句，返回影响的记录数
        /// </summary>
        /// <param name="SQLString">SQL语句</param>
        /// <returns>影响的记录数</returns>
        public static int ExecuteSql(string SQLString)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        int rows = cmd.ExecuteNonQuery();
                        return rows;
                    }
                    catch (MySql.Data.MySqlClient.MySqlException e)
                    {
                        connection.Close();
                        throw e;
                    }
                }
            }
        }

        public static int ExecuteSqlByTime(string SQLString, int Times)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        cmd.CommandTimeout = Times;
                        int rows = cmd.ExecuteNonQuery();
                        return rows;
                    }
                    catch (MySql.Data.MySqlClient.MySqlException e)
                    {
                        connection.Close();
                        throw e;
                    }
                }
            }
        }
      
        /// <summary>
        /// 执行MySql和Oracle滴混合事务
        /// </summary>
        /// <param name="list">SQL命令行列表</param>
        /// <param name="oracleCmdSqlList">Oracle命令行列表</param>
        /// <returns>执行结果 0-由于SQL造成事务失败 -1 由于Oracle造成事务失败 1-整体事务执行成功</returns>
        public static int ExecuteSqlTran(List<CommandInfo> list, List<CommandInfo> oracleCmdSqlList)
        {
            using (MySqlConnection conn = new MySqlConnection(connectionString))
            {
                conn.Open();
                MySqlCommand cmd = new MySqlCommand();
                cmd.Connection = conn;
                MySqlTransaction tx = conn.BeginTransaction();
                cmd.Transaction = tx;
                try
                {
                    foreach (CommandInfo myDE in list)
                    {
                        string cmdText = myDE.CommandText;
                        MySqlParameter[] cmdParms = (MySqlParameter[])myDE.Parameters;
                        PrepareCommand(cmd, conn, tx, cmdText, cmdParms);
                        if (myDE.EffentNextType == EffentNextType.SolicitationEvent)
                        {
                            if (myDE.CommandText.ToLower().IndexOf("count(") == -1)
                            {
                                tx.Rollback();
                                throw new Exception("违背要求"+myDE.CommandText+"必须符合select count(..的格式");
                                //return 0;
                            }

                            object obj = cmd.ExecuteScalar();
                            bool isHave = false;
                            if (obj == null && obj == DBNull.Value)
                            {
                                isHave = false;
                            }
                            isHave = Convert.ToInt32(obj) > 0;
                            if (isHave)
                            {
                                //引发事件
                                myDE.OnSolicitationEvent();
                            }
                        }
                        if (myDE.EffentNextType == EffentNextType.WhenHaveContine || myDE.EffentNextType == EffentNextType.WhenNoHaveContine)
                        {
                            if (myDE.CommandText.ToLower().IndexOf("count(") == -1)
                            {
                                tx.Rollback();
                                throw new Exception("SQL:违背要求" + myDE.CommandText + "必须符合select count(..的格式");
                                //return 0;
                            }

                            object obj = cmd.ExecuteScalar();
                            bool isHave = false;
                            if (obj == null && obj == DBNull.Value)
                            {
                                isHave = false;
                            }
                            isHave = Convert.ToInt32(obj) > 0;

                            if (myDE.EffentNextType == EffentNextType.WhenHaveContine && !isHave)
                            {
                                tx.Rollback();
                                throw new Exception("SQL:违背要求" + myDE.CommandText + "返回值必须大于0");
                                //return 0;
                            }
                            if (myDE.EffentNextType == EffentNextType.WhenNoHaveContine && isHave)
                            {
                                tx.Rollback();
                                throw new Exception("SQL:违背要求" + myDE.CommandText + "返回值必须等于0");
                                //return 0;
                            }
                            continue;
                        }
                        int val = cmd.ExecuteNonQuery();
                        if (myDE.EffentNextType == EffentNextType.ExcuteEffectRows && val == 0)
                        {
                            tx.Rollback();
                            throw new Exception("SQL:违背要求" + myDE.CommandText + "必须有影响行");
                            //return 0;
                        }
                        cmd.Parameters.Clear();
                    }
                    string oraConnectionString = PubConstant.GetConnectionString("ConnectionStringPPC");
                    bool res = OracleHelper.ExecuteSqlTran(oraConnectionString, oracleCmdSqlList);
                    if (!res)
                    {
                        tx.Rollback();
                        throw new Exception("执行失败");
                        // return -1;
                    }
                    tx.Commit();
                    return 1;
                }
                catch (MySql.Data.MySqlClient.MySqlException e)
                {
                    tx.Rollback();
                    throw e;
                }
                catch (Exception e)
                {
                    tx.Rollback();
                    throw e;
                }
            }
        }        
        /// <summary>
        /// 执行多条SQL语句，实现数据库事务。
        /// </summary>
        /// <param name="SQLStringList">多条SQL语句</param>        
        public static int ExecuteSqlTran(List<String> SQLStringList)
        {
            using (MySqlConnection conn = new MySqlConnection(connectionString))
            {
                conn.Open();
                MySqlCommand cmd = new MySqlCommand();
                cmd.Connection = conn;
                MySqlTransaction tx = conn.BeginTransaction();
                cmd.Transaction = tx;
                try
                {
                    int count = 0;
                    for (int n = 0; n < SQLStringList.Count; n++)
                    {
                        string strsql = SQLStringList[n];
                        if (strsql.Trim().Length > 1)
                        {
                            cmd.CommandText = strsql;
                            count += cmd.ExecuteNonQuery();
                        }
                    }
                    tx.Commit();
                    return count;
                }
                catch
                {
                    tx.Rollback();
                    return 0;
                }
            }
        }
        /// <summary>
        /// 执行带一个存储过程参数的的SQL语句。
        /// </summary>
        /// <param name="SQLString">SQL语句</param>
        /// <param name="content">参数内容,比如一个字段是格式复杂的文章，有特殊符号，可以通过这个方式添加</param>
        /// <returns>影响的记录数</returns>
        public static int ExecuteSql(string SQLString, string content)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                MySqlCommand cmd = new MySqlCommand(SQLString, connection);
                MySql.Data.MySqlClient.MySqlParameter myParameter = new MySql.Data.MySqlClient.MySqlParameter("@content", SqlDbType.NText);
                myParameter.Value = content;
                cmd.Parameters.Add(myParameter);
                try
                {
                    connection.Open();
                    int rows = cmd.ExecuteNonQuery();
                    return rows;
                }
                catch (MySql.Data.MySqlClient.MySqlException e)
                {
                    throw e;
                }
                finally
                {
                    cmd.Dispose();
                    connection.Close();
                }
            }
        }
        /// <summary>
        /// 执行带一个存储过程参数的的SQL语句。
        /// </summary>
        /// <param name="SQLString">SQL语句</param>
        /// <param name="content">参数内容,比如一个字段是格式复杂的文章，有特殊符号，可以通过这个方式添加</param>
        /// <returns>影响的记录数</returns>
        public static object ExecuteSqlGet(string SQLString, string content)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                MySqlCommand cmd = new MySqlCommand(SQLString, connection);
                MySql.Data.MySqlClient.MySqlParameter myParameter = new MySql.Data.MySqlClient.MySqlParameter("@content", SqlDbType.NText);
                myParameter.Value = content;
                cmd.Parameters.Add(myParameter);
                try
                {
                    connection.Open();
                    object obj = cmd.ExecuteScalar();
                    if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
                    {
                        return null;
                    }
                    else
                    {
                        return obj;
                    }
                }
                catch (MySql.Data.MySqlClient.MySqlException e)
                {
                    throw e;
                }
                finally
                {
                    cmd.Dispose();
                    connection.Close();
                }
            }
        }
        /// <summary>
        /// 向数据库里插入图像格式的字段(和上面情况类似的另一种实例)
        /// </summary>
        /// <param name="strSQL">SQL语句</param>
        /// <param name="fs">图像字节,数据库的字段类型为image的情况</param>
        /// <returns>影响的记录数</returns>
        public static int ExecuteSqlInsertImg(string strSQL, byte[] fs)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                MySqlCommand cmd = new MySqlCommand(strSQL, connection);
                MySql.Data.MySqlClient.MySqlParameter myParameter = new MySql.Data.MySqlClient.MySqlParameter("@fs", SqlDbType.Image);
                myParameter.Value = fs;
                cmd.Parameters.Add(myParameter);
                try
                {
                    connection.Open();
                    int rows = cmd.ExecuteNonQuery();
                    return rows;
                }
                catch (MySql.Data.MySqlClient.MySqlException e)
                {
                    throw e;
                }
                finally
                {
                    cmd.Dispose();
                    connection.Close();
                }
            }
        }

        /// <summary>
        /// 执行一条计算查询结果语句，返回查询结果（object）。
        /// </summary>
        /// <param name="SQLString">计算查询结果语句</param>
        /// <returns>查询结果（object）</returns>
        public static object GetSingle(string SQLString)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        object obj = cmd.ExecuteScalar();
                        if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
                        {
                            return null;
                        }
                        else
                        {
                            return obj;
                        }
                    }
                    catch (MySql.Data.MySqlClient.MySqlException e)
                    {
                        connection.Close();
                        throw e;
                    }
                }
            }
        }
        public static object GetSingle(string SQLString, int Times)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        cmd.CommandTimeout = Times;
                        object obj = cmd.ExecuteScalar();
                        if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
                        {
                            return null;
                        }
                        else
                        {
                            return obj;
                        }
                    }
                    catch (MySql.Data.MySqlClient.MySqlException e)
                    {
                        connection.Close();
                        throw e;
                    }
                }
            }
        }
        /// <summary>
        /// 执行查询语句，返回MySqlDataReader ( 注意：调用该方法后，一定要对MySqlDataReader进行Close )
        /// </summary>
        /// <param name="strSQL">查询语句</param>
        /// <returns>MySqlDataReader</returns>
        public static MySqlDataReader ExecuteReader(string strSQL)
        {
            MySqlConnection connection = new MySqlConnection(connectionString);
            MySqlCommand cmd = new MySqlCommand(strSQL, connection);
            try
            {
                connection.Open();
                MySqlDataReader myReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                return myReader;
            }
            catch (MySql.Data.MySqlClient.MySqlException e)
            {
                throw e;
            }   

        }
        /// <summary>
        /// 执行查询语句，返回DataSet
        /// </summary>
        /// <param name="SQLString">查询语句</param>
        /// <returns>DataSet</returns>
        public static DataSet Query(string SQLString)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                DataSet ds = new DataSet();
                try
                {
                    connection.Open();
                    MySqlDataAdapter command = new MySqlDataAdapter(SQLString, connection);
                    command.Fill(ds, "ds");
                }
                catch (MySql.Data.MySqlClient.MySqlException ex)
                {
                    throw new Exception(ex.Message);
                }
                return ds;
            }
        }
        public static DataSet Query(string SQLString, int Times)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                DataSet ds = new DataSet();
                try
                {
                    connection.Open();
                    MySqlDataAdapter command = new MySqlDataAdapter(SQLString, connection);
                    command.SelectCommand.CommandTimeout = Times;
                    command.Fill(ds, "ds");
                }
                catch (MySql.Data.MySqlClient.MySqlException ex)
                {
                    throw new Exception(ex.Message);
                }
                return ds;
            }
        }



        #endregion

        #region 执行带参数的SQL语句

        /// <summary>
        /// 执行SQL语句，返回影响的记录数
        /// </summary>
        /// <param name="SQLString">SQL语句</param>
        /// <returns>影响的记录数</returns>
        public static int ExecuteSql(string SQLString, params MySqlParameter[] cmdParms)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand())
                {
                    try
                    {
                        PrepareCommand(cmd, connection, null, SQLString, cmdParms);
                        int rows = cmd.ExecuteNonQuery();
                        cmd.Parameters.Clear();
                        return rows;
                    }
                    catch (MySql.Data.MySqlClient.MySqlException e)
                    {
                        throw e;
                    }
                }
            }
        }


        /// <summary>
        /// 执行多条SQL语句，实现数据库事务。
        /// </summary>
        /// <param name="SQLStringList">SQL语句的哈希表（key为sql语句，value是该语句的MySqlParameter[]）</param>
        public static void ExecuteSqlTran(Hashtable SQLStringList)
        {
            using (MySqlConnection conn = new MySqlConnection(connectionString))
            {
                conn.Open();
                using (MySqlTransaction trans = conn.BeginTransaction())
                {
                    MySqlCommand cmd = new MySqlCommand();
                    try
                    {
                        //循环
                        foreach (DictionaryEntry myDE in SQLStringList)
                        {
                            string cmdText = myDE.Key.ToString();
                            MySqlParameter[] cmdParms = (MySqlParameter[])myDE.Value;
                            PrepareCommand(cmd, conn, trans, cmdText, cmdParms);
                            int val = cmd.ExecuteNonQuery();
                            cmd.Parameters.Clear();
                        }
                        trans.Commit();
                    }
                    catch
                    {
                        trans.Rollback();
                        throw;
                    }
                }
            }
        }
        /// <summary>
        /// 执行多条SQL语句，实现数据库事务。
        /// </summary>
        /// <param name="SQLStringList">SQL语句的哈希表（key为sql语句，value是该语句的MySqlParameter[]）</param>
        public static int ExecuteSqlTran(System.Collections.Generic.List<CommandInfo> cmdList)
        {
            using (MySqlConnection conn = new MySqlConnection(connectionString))
            {
                conn.Open();
                using (MySqlTransaction trans = conn.BeginTransaction())
                {
                    MySqlCommand cmd = new MySqlCommand();
                    try
                    { int count = 0;
                        //循环
                        foreach (CommandInfo myDE in cmdList)
                        {
                            string cmdText = myDE.CommandText;
                            MySqlParameter[] cmdParms = (MySqlParameter[])myDE.Parameters;
                            PrepareCommand(cmd, conn, trans, cmdText, cmdParms);
                           
                            if (myDE.EffentNextType == EffentNextType.WhenHaveContine || myDE.EffentNextType == EffentNextType.WhenNoHaveContine)
                            {
                                if (myDE.CommandText.ToLower().IndexOf("count(") == -1)
                                {
                                    trans.Rollback();
                                    return 0;
                                }

                                object obj = cmd.ExecuteScalar();
                                bool isHave = false;
                                if (obj == null && obj == DBNull.Value)
                                {
                                    isHave = false;
                                }
                                isHave = Convert.ToInt32(obj) > 0;

                                if (myDE.EffentNextType == EffentNextType.WhenHaveContine && !isHave)
                                {
                                    trans.Rollback();
                                    return 0;
                                }
                                if (myDE.EffentNextType == EffentNextType.WhenNoHaveContine && isHave)
                                {
                                    trans.Rollback();
                                    return 0;
                                }
                                continue;
                            }
                            int val = cmd.ExecuteNonQuery();
                            count += val;
                            if (myDE.EffentNextType == EffentNextType.ExcuteEffectRows && val == 0)
                            {
                                trans.Rollback();
                                return 0;
                            }
                            cmd.Parameters.Clear();
                        }
                        trans.Commit();
                        return count;
                    }
                    catch
                    {
                        trans.Rollback();
                        throw;
                    }
                }
            }
        }
        /// <summary>
        /// 执行多条SQL语句，实现数据库事务。
        /// </summary>
        /// <param name="SQLStringList">SQL语句的哈希表（key为sql语句，value是该语句的MySqlParameter[]）</param>
        public static void ExecuteSqlTranWithIndentity(System.Collections.Generic.List<CommandInfo> SQLStringList)
        {
            using (MySqlConnection conn = new MySqlConnection(connectionString))
            {
                conn.Open();
                using (MySqlTransaction trans = conn.BeginTransaction())
                {
                    MySqlCommand cmd = new MySqlCommand();
                    try
                    {
                        int indentity = 0;
                        //循环
                        foreach (CommandInfo myDE in SQLStringList)
                        {
                            string cmdText = myDE.CommandText;
                            MySqlParameter[] cmdParms = (MySqlParameter[])myDE.Parameters;
                            foreach (MySqlParameter q in cmdParms)
                            {
                                if (q.Direction == ParameterDirection.InputOutput)
                                {
                                    q.Value = indentity;
                                }
                            }
                            PrepareCommand(cmd, conn, trans, cmdText, cmdParms);
                            int val = cmd.ExecuteNonQuery();
                            foreach (MySqlParameter q in cmdParms)
                            {
                                if (q.Direction == ParameterDirection.Output)
                                {
                                    indentity = Convert.ToInt32(q.Value);
                                }
                            }
                            cmd.Parameters.Clear();
                        }
                        trans.Commit();
                    }
                    catch
                    {
                        trans.Rollback();
                        throw;
                    }
                }
            }
        }
        /// <summary>
        /// 执行多条SQL语句，实现数据库事务。
        /// </summary>
        /// <param name="SQLStringList">SQL语句的哈希表（key为sql语句，value是该语句的MySqlParameter[]）</param>
        public static void ExecuteSqlTranWithIndentity(Hashtable SQLStringList)
        {
            using (MySqlConnection conn = new MySqlConnection(connectionString))
            {
                conn.Open();
                using (MySqlTransaction trans = conn.BeginTransaction())
                {
                    MySqlCommand cmd = new MySqlCommand();
                    try
                    {
                        int indentity = 0;
                        //循环
                        foreach (DictionaryEntry myDE in SQLStringList)
                        {
                            string cmdText = myDE.Key.ToString();
                            MySqlParameter[] cmdParms = (MySqlParameter[])myDE.Value;
                            foreach (MySqlParameter q in cmdParms)
                            {
                                if (q.Direction == ParameterDirection.InputOutput)
                                {
                                    q.Value = indentity;
                                }
                            }
                            PrepareCommand(cmd, conn, trans, cmdText, cmdParms);
                            int val = cmd.ExecuteNonQuery();
                            foreach (MySqlParameter q in cmdParms)
                            {
                                if (q.Direction == ParameterDirection.Output)
                                {
                                    indentity = Convert.ToInt32(q.Value);
                                }
                            }
                            cmd.Parameters.Clear();
                        }
                        trans.Commit();
                    }
                    catch
                    {
                        trans.Rollback();
                        throw;
                    }
                }
            }
        }
        /// <summary>
        /// 执行一条计算查询结果语句，返回查询结果（object）。
        /// </summary>
        /// <param name="SQLString">计算查询结果语句</param>
        /// <returns>查询结果（object）</returns>
        public static object GetSingle(string SQLString, params MySqlParameter[] cmdParms)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand())
                {
                    try
                    {
                        PrepareCommand(cmd, connection, null, SQLString, cmdParms);
                        object obj = cmd.ExecuteScalar();
                        cmd.Parameters.Clear();
                        if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
                        {
                            return null;
                        }
                        else
                        {
                            return obj;
                        }
                    }
                    catch (MySql.Data.MySqlClient.MySqlException e)
                    {
                        throw e;
                    }
                }
            }
        }

        /// <summary>
        /// 执行查询语句，返回MySqlDataReader ( 注意：调用该方法后，一定要对MySqlDataReader进行Close )
        /// </summary>
        /// <param name="strSQL">查询语句</param>
        /// <returns>MySqlDataReader</returns>
        public static MySqlDataReader ExecuteReader(string SQLString, params MySqlParameter[] cmdParms)
        {
            MySqlConnection connection = new MySqlConnection(connectionString);
            MySqlCommand cmd = new MySqlCommand();
            try
            {
                PrepareCommand(cmd, connection, null, SQLString, cmdParms);
                MySqlDataReader myReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                cmd.Parameters.Clear();
                return myReader;
            }
            catch (MySql.Data.MySqlClient.MySqlException e)
            {
                throw e;
            }
            //            finally
            //            {
            //                cmd.Dispose();
            //                connection.Close();
            //            }    

        }

        /// <summary>
        /// 执行查询语句，返回DataSet
        /// </summary>
        /// <param name="SQLString">查询语句</param>
        /// <returns>DataSet</returns>
        public static DataSet Query(string SQLString, params MySqlParameter[] cmdParms)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                MySqlCommand cmd = new MySqlCommand();
                PrepareCommand(cmd, connection, null, SQLString, cmdParms);
                using (MySqlDataAdapter da = new MySqlDataAdapter(cmd))
                {
                    DataSet ds = new DataSet();
                    try
                    {
                        da.Fill(ds, "ds");
                        cmd.Parameters.Clear();
                    }
                    catch (MySql.Data.MySqlClient.MySqlException ex)
                    {
                        throw new Exception(ex.Message);
                    }
                    return ds;
                }
            }
        }


        private static void PrepareCommand(MySqlCommand cmd, MySqlConnection conn, MySqlTransaction trans, string cmdText, MySqlParameter[] cmdParms)
        {
            if (conn.State != ConnectionState.Open)
                conn.Open();
            cmd.Connection = conn;
            cmd.CommandText = cmdText;
            if (trans != null)
                cmd.Transaction = trans;
            cmd.CommandType = CommandType.Text;//cmdType;
            if (cmdParms != null)
            {


                foreach (MySqlParameter parameter in cmdParms)
                {
                    if ((parameter.Direction == ParameterDirection.InputOutput || parameter.Direction == ParameterDirection.Input) &&
                        (parameter.Value == null))
                    {
                        parameter.Value = DBNull.Value;
                    }
                    cmd.Parameters.Add(parameter);
                }
            }
        }

        #endregion

        

    }

}