*.ashx文件不能访问Session值的解决方法

<%@ WebHandler Language="C#" Class="productHandler" %>using System; using System.Web; using JBTCard.Entity.CompanyEntity; using JBTCard.Business.CompanyBS; using System.Collections.Generic; using Newtonsoft.Json; using System.Web.SessionState; public class productHandler : IHttpHandler, IRequiresSessionState, IReadOnlySessionState{     public void ProcessRequest (HttpContext context) {   string moduleId = context.Request.Form["moduleId"].ToString();   string message = "";   switch (moduleId)   {   case "getPTypeList":   IList<ProductTypeIdNameEntity> list = ProductTypeBS.GetPTypeListIdName();   message = JavaScriptConvert.SerializeObject(list);   break;   case "getCompanyById": int cid = Convert.ToInt32(context.Session["cid"]);  CompanyEntity company = CompanyBS.GetCompanyEntyById(1);   message = JavaScriptConvert.SerializeObject(company);   break;   case "insert":   string condis = context.Request.Form["condi"].ToString();   ProductEntity model = (ProductEntity)JavaScriptConvert.DeserializeObject(condis, typeof(ProductEntity));   bool b = ProductBS.AddProduct(model);   if (b)   {   message = "{success:true}";   }   else   {   throw new Exception("商品添加失败！");   } break;   }   context.Response.ContentType = "text/javascript";   context.Response.Write(message);   }   public bool IsReusable {     get {       return false;     }   } }

using System.Web.SessionState;