Visual Studio无法识别新类

I'm using visual studio 2008 SP1, I'm working with a web project in VB.NET. the problem when I add new class file (of-course in App_Code) it doesn't recognize it. all the old class files are working fine, but the new ones aren't. I restarted my computer and still the same problem.I'm using visual studio 2008 SP1, I'm working w