在类项目中读取asp.net中的web.config数据库链接

Class1.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ClassLibrary1
{
    public class Class1
    {
        public string testconSQL()
        {
            string conSQL = System.Configuration.ConfigurationSettings.AppSettings["mySystem"].ToString();
            return conSQL;
        }
    }
    
}

 
asp.net web.config

  <appSettings>
    <add key="mySystem" value="server=localhost;uid=sa;pwd=123;database=mySystemDataBase" />
  </appSettings>

Default.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using ClassLibrary1;

namespace WebApplication1
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Class1 aa = new Class1();
            Response.Write(aa.testconSQL());
        }
    }
}