在构建ASP时可能导致错误的原因是什么?. NET web应用程序

当我构建我的解决方案时，它显示以下错误:

包含。HttpRequest'没有包含'RequestContext'的定义，也没有扩展方法'RequestContext'接受类型为'System.Web '的第一个参数。HttpRequest'可以找到(你缺少using指令或程序集引用吗?)

我缺少什么dll或引用!

代码:

 public void ProcessRequest(HttpContext context)
    {
        try
        {
            HttpRequest request = context.Request;
            string methodName = "";
            if (request.RequestContext.RouteData.Values["methodName"] != null)
            {
                methodName = request.RequestContext.RouteData.Values["methodName"].ToString();
            }
            else
            {
                methodName = request.RawUrl.Substring(request.RawUrl.LastIndexOf("/") + 1);
            }
            //if form post was made way to get values
            //context.Request.Form["firstName"]; //parameter key
            string json = new System.IO.StreamReader(context.Request.InputStream).ReadToEnd();
            JavaScriptSerializer jss = new JavaScriptSerializer();
            ServiceProcesser process = new ServiceProcesser(typeof(AspxCommerce.AdminNotification.AdminNotificationController), json, methodName);
            var response = process.Invoke();
            if (response != null)
            {
                context.Response.ContentType = "application/json";
                context.Response.Write(jss.Serialize(new { d = response }));
            }
            else
            {
                context.Response.ContentType = "application/json";
                context.Response.Write(jss.Serialize(new { d = "" }));
            }
        }
        catch (Exception ex)
        {
            JavaScriptSerializer jss = new JavaScriptSerializer();
            context.Response.ContentType = "application/json";
            var resp = new { d = ex.Message.ToString() };
            context.Response.Write(jss.Serialize(resp));
        }
    }

完整的源代码，你可以探索我的github repo:https://github.com/Milstein/Ratamata