asp.net数据库操作类

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

namespace SystemDAL
{
    #region 数据库层操作类
    public class SqlHelper
    {
        /// <summary>
        /// 添加 修改 删除所用的方法
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="commandtype"></param>
        /// <param name="parameters"></param>
        /// <returns>rowscount</returns>
        public static int ExecuteNonQuery(string sql, CommandType commandtype, params SqlParameter[] parameters)
        {
            SqlCommand cmd = GetCommand(sql, commandtype, parameters);
            int rowscount = cmd.ExecuteNonQuery();      //返回受影响的行数
            cmd.Parameters.Clear();          //移除对象
            cmd.Connection.Close();          //关闭数据库连接
            return rowscount;
        }

        /// <summary>
        /// 一个被重用的得到Command命令对象的方法
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="commandtype"></param>
        /// <param name="parameters"></param>
        /// <returns>cmd</returns>
        private static SqlCommand GetCommand(string sql, CommandType commandtype, params SqlParameter[] parameters)
        {
            GetConnectionString Opencon = new GetConnectionString();
            Opencon.OpenDataBase();
            SqlConnection conn = Opencon.m_objConnection;
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = conn;
            cmd.CommandType = commandtype;
            cmd.CommandText = sql;
            if (parameters != null)
            {
                foreach (SqlParameter p in parameters)
                {
                    cmd.Parameters.Add(p);
                }
            }
            //cmd.Connection.Open();
            return cmd;
        }

        /// <summary>
        /// 查询返回一行一列的值
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="commandtype"></param>
        /// <param name="parameters"></param>
        /// <returns>result</returns>
        public static object ExecuteScalar(string sql, CommandType commandtype, params SqlParameter[] parameters)
        {
            SqlCommand cmd = GetCommand(sql, commandtype, parameters);
            object result = cmd.ExecuteScalar();
            cmd.Parameters.Clear();
            cmd.Connection.Close();
            return result;

        }

        /// <summary>
        /// 查询得到Datareader
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="commandtype"></param>
        /// <param name="parameters"></param>
        /// <returns>dr</returns>
        public static SqlDataReader ExecuteReader(string sql, CommandType commandtype, params SqlParameter[] parameters)
        {
            SqlCommand cmd = GetCommand(sql, commandtype, parameters);
            //SqlDataReader dr = cmd.ExecuteReader();
            SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
            cmd.Parameters.Clear();
            return dr;
        }   
    }
    #endregion
}