解决ashx文件下的Session“未将对象引用设置到对象的实例”

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using PPT_DAL;
namespace PPT_Web.tool
{
/// <summary>
/// Login 的摘要说明
/// </summary>
public class Login : IHttpHandler
{

public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "text/html";
string lo_usm = context.Request.Params["lo_usm"];
string lo_pwd = context.Request.Params["lo_pwd"];
UserEntity userModel = PPT_BLL.UserManager.Login(lo_usm,lo_pwd);
if (userModel != null)
{
context.Session["UserId"] = userModel.USR_ID;
context.Response.Write("{'result':'1'}");
}
else
{
context.Response.Write("{'result':'0'}");
}
}

public bool IsReusable
{
get
{
return false;
}
}
}
}

问题：

　　如题所示，在一般处理程序文件，即ashx文件下调用Session["UserId"],当调试的时候会显示“未将对象实例化的”的错误

解决方法：

　　将该类实现“IRequiresSessionState”的接口即可，而此接口在System.Web.SessionState命名空间下，所以要在上面添加一句：using System.Web.SessionState;

　　最终实现代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using PPT_DAL;
using System.Web.SessionState;
namespace PPT_Web.tool
{
/// <summary>
/// Login 的摘要说明
/// </summary>
public class Login : IHttpHandler, IRequiresSessionState
{

public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "text/html";
string lo_usm = context.Request.Params["lo_usm"];
string lo_pwd = context.Request.Params["lo_pwd"];
UserEntity userModel = PPT_BLL.UserManager.Login(lo_usm,lo_pwd);
if (userModel != null)
{
context.Session["UserId"] = userModel.USR_ID;
context.Response.Write("{'result':'1'}");
}
else
{
context.Response.Write("{'result':'0'}");
}
}

public bool IsReusable
{
get
{
return false;
}
}
}
}