SQLHelper类

　　在我们编写数据访问层DAL时，常常需要编写一个SQLHelper类，方便其他的数据库表类调用，下面就是一个实现了可以传递sql语句来增删改查得类：

using System;
using System.Collections.Generic;
using System.Text;
using System.Data.SqlClient;
using System.Data;

using System.Configuration;

namespace DAL
{
    public class SQLHelper
    {
        private SqlConnection conn = null;
        private SqlCommand comm = null;
        private SqlDataReader sdr = null;

        public SQLHelper()
        {
            string connStr = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString;
            conn = new SqlConnection(connStr);
        }

        private SqlConnection GetConn()
        {
            if (conn.State == ConnectionState.Closed)
            {
                conn.Open();
            }
            return conn;
        }

        /// <summary>
        /// 执行不带sql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</param>
        /// <param name="ct">命令类型</param>
        /// <returns></returns>
        public int ExecuteNonQuery(string cmdText, CommandType ct)
        {
            using (comm = new SqlCommand(cmdText,GetConn()))
            {
                comm.CommandType = ct;
                int res = comm.ExecuteNonQuery();
                return res;                
            }
        }

        /// <summary>
        /// 执行带有sql参数的增删改sql语句或存储过程
        /// </summary>
        /// <param name="cmdText">sql语句或者存储过程</param>
        /// <param name="paras">sql语句参数或存储过程参数</param>
        /// <param name="ct">命令类型</param>
        /// <returns></returns>
        public int ExecuteNonQuery(string cmdText, SqlParameter[] paras, CommandType ct)
        {
            using (comm = new SqlCommand(cmdText,GetConn()))
            {
                comm.CommandType = ct;
                comm.Parameters.AddRange(paras);
                int res = comm.ExecuteNonQuery();
                return res;                
            }
        }

      /// <summary>
        /// 执行不带sql参数的sql查询语句或存储过程
        /// </summary>
        /// <param name="cmdText">sql查询语句或存储过程</param>
        /// <param name="ct">命令类型</param>
        /// <returns>数据表</returns>
        public DataTable ExecuteQuery(string cmdText,CommandType ct)
        {
            comm = new SqlCommand(cmdText, GetConn());
            comm.CommandType = ct;
            DataTable dt = new DataTable();
            using (sdr = comm.ExecuteReader(CommandBehavior.CloseConnection))
            {
                dt.Load(sdr);
            }
            return dt;            
        }

        /// <summary>
        /// 执行带有sql参数的sql查询语句或存储过程
        /// </summary>
        /// <param name="cmdText">sql查询语句或存储过程</param>
        /// <param name="paras">sql参数</param>
        /// <param name="ct">命令类型</param>
        /// <returns>数据表</returns>
        public DataTable ExcuteQuery(string cmdText, SqlParameter[] paras, CommandType ct)
        {
            comm = new SqlCommand(cmdText, GetConn());
            comm.CommandType = ct;
            comm.Parameters.AddRange(paras);
            DataTable dt = new DataTable();
            using (sdr = comm.ExecuteReader(CommandBehavior.CloseConnection))
            {
                dt.Load(sdr);
            }
            return dt;
        }

    }
}