Error message in VS2008

[wesbird]

Hi,
I just upgrade my AutoCAD .Net application from AutoCAD 2006 + .net 1.1 + Visual Studio 2003 to AutoCAD 2008 + .net 2.0 + Visual Studio 2008. When I open my solution, there must be a new feature in VS2008, my application will get compiled automatically in the background, so it show some errors. error message attached at the end of post. When I select Build or Rebuild, there are no error at all.
So what's this problem, how I can fix it.


Error message:
'Autodesk.AutoCAD.DatabaseServices.ObjectIdCollection' does not contain a definition for 'Count' and no extension method 'Count' accepting a first argument of type 'Autodesk.AutoCAD.DatabaseServices.ObjectIdCollection' could be found (are you missing a using directive or an assembly reference?)
'Autodesk.AutoCAD.EditorInput.SelectionSet' does not contain a definition for 'Count' and no extension method 'Count' accepting a first argument of type 'Autodesk.AutoCAD.EditorInput.SelectionSet' could be found (are you missing a using directive or an assembly reference?)



Thank you,
Wes