asxh中读取Session值为空引用问题

//在ashx文件中读写session

//晕Ｓ，终于搞定在ashx中输出验证码，在保存验证码时竟然读不到session
//错误提示：未将对象引用设置到对象的实例。
//查找资料终于搞定....
 
//首先要继承 System.Web.SessionState.IReadOnlySessionState 的接口
//其中：System.Web.SessionState.IReadOnlySessionState为只读会话的接口
 
//而：System.Web.SessionState.IRequiresSessionState　为可读可写会话的接口，这个看情况而继承吧～～～
 
代码如下：
 
 using System
 using System.Web
 using System.Web.SessionState
 Public Class myVerifyCode : Implements IHttpHandler, IRequiresSessionState
   
   
    Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
 
        context.Session("VerifyCode") = "登陆成功"
        context.Response.Write(context.Session("VerifyCode"))

   End Sub
 
    Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
        Get
            Return True
        End Get
    End Property

End Class