ObjectDataSource cannot detect any new [DataObjectMethods] added to the DLL

Hello,
  My issue is that I have a Class Library project that performs  business services. This dll contains methods marked with [DataObjectMethod( ....)] attributes. When I first time had added reference to this Dll from the ASP.NET project, the ObjectDataSources were able to detect all my methods from the business service dll, but when I have added several new methods to the dll [ also marked with [DataObjectMethod attributes], the ObjectDataSources on the ASP.NET pages only detect old ones, but not newly added.

 So I decided to remove reference to this DLL from the ASP.NET project. I was able to delete it, then I rebuild the whole solution and when I tried to add this reference back, I get the Message that this reference is already added. Again my ObjectDataSources just do not "see" any new methods from the updated DLL!!!

It really drives me nuts. Why I just cannot remove the reference, recompile both DLL and ASP.NET, then add this reference and use my updated DLL???? Please help!