appel form c#

If the question is how to show a form then Doha Msg's response is the likely solution. If the question is how to call a method in a form, then creating another instance of the form, as the code in Doha Msg's response does, then that will not work.

English Question: How to call forms from button ?

Answer: in the button click event, write a code similar to
           MyForm frm = new MyForm();
            frm.Show(); // or frm.ShowDialog();

Where MyForm is the Class defining your form. If you use .Net 4.0 you can instantiate the form like this : var frm = new MyForm();