C#:SqlConnection 当前上下文中不存在名称SqlHelper

using System;
using System.Data;
using System.Data.SqlClient;
using System.Collections.Generic;
using System.Linq;
using System.Web.Security;
using System.Configuration;

/// <summary>
///Msg 的摘要说明
/// </summary>
public class Msg
{
private const string SQL_PARM_RECEIVE = "@receive";
private const string SQL_PARM_SEND = "@SEND";
private const string SQL_PARM_TITLE = "@title";
private const string SQL_PARM_CONTENT = "@content";
private const string SQL_INSERT_MESSAGE = "INSERT INTO message VALUES(@receive,@send,@title,@content,'0')";
public Msg()
{
//
//TODO: 在此处添加构造函数逻辑
//
}

public bool SendMSG(string receive, string send, string title, string content)
{
if (Membership.FindUsersByName(receive) == null)
return false;
else
{
SqlParameter[

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