Entity Framework Detecting Changes

I am currently using the entity framework as a data layer for an application.  I am still learning the EF so i might have some of the nameing conventions off.

I have a context Person object that i am displaying to the user via a group of bound controls.  When the user closed the form i would like to detect whether any changes have been made to the object.  If there have been, then i will prompt them to save the changes.

I have everything working well, but i can't seem to figure out how to detect if the object has changed.  I see that my Context Object has a .DetectChanges, but that doesn't seem to return what i would expect.

Is there a way to tell whether changes has been made to an object in the EF?

Thanks in advance.