Dataset HasChanges method - command button vs menu item

I have a winform app containing a datagridview, a command button and a menu bar with an item for searching.

The datagridview is bound to a dataset.  If I change the contents of a cell, then click on the command button, the HasChanges method fires for the dataset.  I expect this.

If I change the contents of the cell, then click on the Search menu item, the HasChanges method does not fire.  I expect the HasChanges method to fire but it does not.  It always returns False.

Is there something different about the way a method responds when you click on a command button versus a menu item?  I assumed they would behave basically the same.

Kris Hood