using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using MySql.Data.MySqlClient;
using System.Configuration;
using System.Data;
/**
 *创建人：LK
 *说明：数据库封装类
 */
namespace MySql
{
    public class MySQlHelper
    {
        private MySqlConnection conn = null;
        private MySqlCommand cmd = null;
        private MySqlDataReader sdr;
        private MySqlDataAdapter sda = null;
        public MySQlHelper() {
            string connStr = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString; //获取MySql数据库连接字符串
            conn = new MySqlConnection(connStr); //数据库连接
        }
        #region
        /// <summary>
        /// 打开数据库链接
        /// </summary>
        /// <returns></returns>
        #endregion
        private MySqlConnection GetConn() { 
        if(conn.State== ConnectionState.Closed)
        {
            conn.Open();
        }
        return conn;
        }
        #region
        /// <summary>
        ///  关闭数据库链接
        /// </summary>
        #endregion
        private void GetConnClose()
        {
            if (conn.State == ConnectionState.Open)
            {
                conn.Close();
            }
        }
        #region
        /// <summary>
        /// 执行不带参数的增删改SQL语句或存储过程
        /// </summary>
        /// <param name="cmdText">增删改SQL语句或存储过程的字符串</param>
        /// <param name="ct">命令类型</param>
        /// <returns>受影响的函数</returns>
        #endregion
        public int ExecuteNonQuery(string cmdText,CommandType ct) {
            int res;
            using(cmd = new MySqlCommand(cmdText,GetConn()))
            {
                cmd.CommandType = ct;
                res = cmd.ExecuteNonQuery();
            }
            return res;
        }
        #region
        /// <summary>
        /// 执行带参数的增删改SQL语句或存储过程
        /// </summary>
        /// <param name="cmdText">增删改SQL语句或存储过程的字符串</param>
        /// <param name="paras">往存储过程或SQL中赋的参数集合</param>
        /// <param name="ct">命令类型</param>
        /// <returns>受影响的函数</returns>
        #endregion
        public int ExecuteNonQuery(string cmdText,MySqlParameter[] paras,CommandType ct)
        {
            int res;
            using(cmd = new MySqlCommand(cmdText,GetConn()))
            {
                cmd.CommandType = ct;
                cmd.Parameters.AddRange(paras);
                res = cmd.ExecuteNonQuery();    
            }
            return res;
        }
        #region
        /// <summary>
        /// 执行不带参数的查询SQL语句或存储过程
        /// </summary>
        /// <param name="cmdText">查询SQL语句或存储过程的字符串</param>
        /// <param name="ct">命令类型</param>
        /// <returns>查询到的DataTable对象</returns>
        #endregion
        public DataTable ExecuteQuery(string cmdText,CommandType ct)
        {
            DataTable dt = new DataTable();
            cmd = new MySqlCommand(cmdText,GetConn());
            cmd.CommandType = ct;
            using(sdr = cmd.ExecuteReader(CommandBehavior.CloseConnection))
            {
                dt.Load(sdr);
            }
            return dt;
        }
        #region
        /// <summary>
        /// 执行带参数的查询SQL语句或存储过程
        /// </summary>
        /// <param name="cmdText">查询SQL语句或存储过程的字符串</param>
        /// <param name="paras">参数集合</param>
        /// <param name="ct">命令类型</param>
        /// <returns></returns>
        #endregion
        public DataTable ExecuteQuery(string cmdText,MySqlParameter[] paras,CommandType ct) 
        {
            DataTable dt = new DataTable();
            cmd = new MySqlCommand(cmdText,GetConn());
            cmd.CommandType = ct;
            cmd.Parameters.AddRange(paras);
            using(sdr = cmd.ExecuteReader(CommandBehavior.CloseConnection))
            {
                dt.Load(sdr);
            }
            return dt;
        }
        #region
        /// <summary>
        /// 执行指定数据库连接字符串的命令,返回DataSet.
        /// </summary>
        /// <param name="strSql">一个有效的数据库连接字符串</param>
        /// <returns>返回一个包含结果集的DataSet</returns>
        #endregion
        public DataSet ExecuteDataset(string strSql)
        {
            DataSet ds = new DataSet();
            sda = new MySqlDataAdapter(strSql,GetConn());
            try
            {
                sda.Fill(ds);
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally {
                GetConnClose();
            }
            return ds;
        }
    }
}

在举例子之前必须懂得两种概念

1、带参数的查询例子

public DataTable SelectByNewsId(string Id)  
            {  
                MySQlHelper h = new MySQlHelper();
                DataTable dt = new DataTable();  
                string sql = "select * from comment where newsId=@Id order by createTime desc";  
                SqlParameter[] paras = new SqlParameter[]  
                {  
                     new SqlParameter ("@newsId",Id )  
                };  
                dt = h.ExecuteQuery(sql, paras, CommandType.Text);  
                return dt;  
            }  

public DataTable SelectByNewsId(string Id)  
            {  
                MySqlHelper h = new MyHelper();
                DataTable dt = new DataTable();  
                string sql = "select * from comment where newsId=‘Id‘ order by createTime desc";  
                dt = sqlhelper.ExecuteQuery(sql,CommandType.Text);  
                return dt;  
            }  

 public Boolean Delete(stringId)  //插入、修改也如此
            {  
                Boolean flag = false;  
                MyHelper h = new MyHelper();
                string sql = "delete from comment where newsId=@Id";  
                SqlParameter[] paras = new SqlParameter[]  
                {  
                    new SqlParameter ("newsId",Id )  
      
                };  
                int res = sqlhelper.ExecuteNonQuery(sql, paras, CommandType.Text);  
                if (res > 0)  
                {  
                    flag = true;  
                }  
                return flag;  
            }  

public Boolean Delete(string Id)  //插入、修改也如此
            {  
                Boolean flag = false;  
                MyHelper h = new MyHelper();
                string sql = "delete from comment where newsId=‘Id‘";  
                int res = sqlhelper.ExecuteNonQuery(sql,  CommandType.Text);  
                if (res > 0)  
                {  
                    flag = true;  
                }  
                return flag;  
            }