C# Label Text Not Updating

You're performing a lengthy operation on the UI thread. You should move it to a background thread (via BackgroundWorker for instance) so the UI thread can do things like repaint the screen when needed. You can cheat and execute Application.DoEvents, but I'd really recommend against it.

This question and answer are basically what you're asking:
Form Not Responding when any other operation performed in C#

use Label.Refresh(); it saves a lot of time.This should work for u

The Label doesn't re-paint until you give the UI thread back to the message loop. Try Label.Refresh, or better yet, try putting your lengthy operation in a background thread as other posters have suggested.