How do I change a image on a Button using Windows Forms?

Question

How do I toggle between two images on a Button? I have a "Lock" and "Unlock" image I would like to use on the same button.

So far I have used the property window to set a single image..

UPDATE: Many good answers, but I should have mention that my two images is in the Property folder. How do I access them with a relative path?

Answer 1

Easy:

button1.Image = System.Drawing.Image.FromFile(@"C:\Users\Administrator\Pictures\forestfloor.jpg");

P.S. Before set image, check if it exist