How to disable the parent form when a child form is active?

Question

How to disable a parent form when child form is active using c#?

Answer 1

Are you calling ShowDialog() or just Show() on your child form from the parent form?

ShowDialog will "block" the user from interacting with the form which is passed as a parameter to ShowDialog.

Within the parent you might call something like:

MyChildForm childForm = new MyChildForm();

childForm.ShowDialog(this);

where this is the parent form.