Refresh DataGridView

Question

Hi,
I try to do project in C# that work with a database, and have a MainForm with a datagridview (display the data from the database).
and have other form, AddForm, that i run it from the MainForm and add a list to the database.
the problem i see when i added a new list to the database (with AddForm form) and close the form the DateGridView can't updated!! 
I tried to do refresh to the datagridview and to the form, but nothing succeed.
note: when i close the program (MainForm) and run it i see the new list found into the datagridview!!