want to know why LoadWithPartialName is deprecated?

Because Suzanne said so.  Or, well, to be more accurate, because it really was the right change to make.

23:43 [ d2d_zZzz] why the hell is Assembly.LoadWithPartialName flagged as obsolete?
23:49 [ Flav] d2d_zZzz: http://blogs.msdn.com/suzcook/archive/2003/05/30/57159.aspx

It’s exactly the kind of problem where your first thought is the wrong one – initially partial loading looks like a real time-and-effort saver and helps ease development and deployment issues.  The path to Dll Hell is paved with API’s with good intentions, after all.