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   源码介绍

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需要引用 MySql.Data.MySqlClient.dll,引用方法可 Install-Package MySql.Data -Version 8.0.13

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Linq;
using System.Web;
using System.Data;
using MySql.Data.MySqlClient;
using System.Configuration;
using System.Data.Common;
using System.Collections.Generic;

namespace wx_webapi.ajax
{
    public class DbHelper
    {
        public static string connectionString = System.Configuration.ConfigurationSettings.AppSettings["ConnectionString"];
        public DbHelper()
        {
 
        }
        #region 公用方法
        /// <summary>
        /// 得到最大值
        /// </summary>
        /// <param name="FieldName"></param>
        /// <param name="TableName"></param>
        /// <returns></returns>
        public  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  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  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  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  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>
        /// 执行多条SQL语句，实现数据库事务。
        /// </summary>
        /// <param name="SQLStringList">多条SQL语句</param>    
        public  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  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  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  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  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  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  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  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  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  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  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  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  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  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
    }
}