Getting size of class

If this is for interop, and you need the size that the object will be when it is marshalled to unmanaged code, then you can use:

Marshal.SizeOf( typeof( <classname> ) );

I've toyed with methods for getting the size of simple objects (as of yet I have found no good way to do this for more complex types short of marking them as MBR and using the method mentioned above). my interest has been in pinning the object and zeroing its memory (this need has largely been eliminated by the SecureString class)

here is what I have for simple types (hopefully it points you in the right direction)
http://stand__sure.aspfreeserver.com/sizeof/utility.vb.html