How to set Shadow to NSWindow?

I worked with NSWindow and i have one problems. I have two windows (ares NSWindows type). From window1, I call NSApplication.SharedApplication.RunModalForWindow(window2); to show window2 (NSWindow)

But I can not set shadown for window2.

I try with this code: HasShadown = true; but don't work.

How to do that?

Please help me!

Thanks so much :)