C# error: InvalidOperationException: Stack empty

问题:

I have been working with a web application. It was running fun until I changed tables which were behind the app. I checked my code, and it looked fine to me. But I am keep getting this error, and not sure why. Can someone help?

[InvalidOperationException: Stack empty.]

System.Collections.Generic.Stack`1.Pop() +8625191

System.Web.UI.RenderTraceListenerList.EndRendering(TextWriter writer, Object renderedObject) +90

System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) [phone]

System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5363

I think these two lines are causing the problem, but it worked fine before I adjust the typelist.

Context<TypedList> GetProductSearch(IPredicateExpression filter);
Context<TypedList> GetProductSearch(IPredicateExpression filter, ISortExpression sorter);