添加命名空间using System.Web.SessionState;
其中：System.Web.SessionState.IReadOnlySessionState 为只读会话的接口;System.Web.SessionState.IRequiresSessionState 为可读可写会话的接口
public class GoodAnswer : IHttpHandler, IRequiresSessionState//接口
{
if (HttpContext.Current.Session["serverCode"].ToString() == servercode)
return "1";
}