SqlHelper.cs

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

namespace _001
{
    public static class SqlHelper
    {
        //定义一个连接字符串,
        //readonly，只能在初始化和构造函数中赋值
        private static readonly string conStr=ConfigurationManager.ConnectionStrings["mssqlserver"].ConnectionString;

        //1.执行增insert 删delete 改update的方法;
        public static int ExecuteNonQuery(string sql,params SqlParameter[] pms)
        {
            using (SqlConnection conn = new SqlConnection(conStr))
            {
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    if (pms != null)
                    {
                        cmd.Parameters.AddRange(pms);
                    }
                    conn.Open();
                    return cmd.ExecuteNonQuery();
                }
            }
        }

        //2.执行查询，返回单个值的方法
        //ExecuteScalar()
        public static object ExecuteScalar(string sql, params SqlParameter[] pms)
        {
            using (SqlConnection conn = new SqlConnection(conStr))
            {
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    if (pms != null)
                    {
                        cmd.Parameters.AddRange(pms);
                    }
                    conn.Open();
                    return cmd.ExecuteScalar();
                }
            }
        }

        //3.执行查询，返回多行，多列的方法
        //ExecuteReader
        public static SqlDataReader ExecuteReader(string sql, params SqlParameter[] pms)
        {
            SqlConnection conn = new SqlConnection(conStr);
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    if (pms != null)
                    {
                        cmd.Parameters.AddRange(pms);
                    }
                    try
                    {
                        conn.Open();
                        return cmd.ExecuteReader(CommandBehavior.CloseConnection);
                    }
                    catch
                    {
                        conn.Close();
                        conn.Dispose();
                        throw;
                    }
                }
        }
    }
}