When would I need to call form.ShowDialog(IWin32Window) rather than form.ShowDialog()?

Question

I have some code, which calls the form.ShowDialog(IWin32Window) overload rather than the form.ShowDialog() one, but which passes in the current active window as the parameter.

Using the other overload seems to leave the behaviour intact. Is it safe to switch to the simpler overload? When would I want to pass in the IWin32Window parameter?

Answer 1

You can use the IWin32Window parameter if you want to parent your form in another application or form.

So for example you can get the handle of another application or form and show your form as a part of that application. You can find more information here

Answer 2

You should use the void constructor under normal circumstances. Like Nathan said, only use the IWin32Window constructor if you want to show the dialog with a specific owner. Which is not typically necessary.

The documentation for ShowDialog() states, "Shows the form as a modal dialog box with the currently active window set as its owner." So, unless you explicitly need to set the owner of a form to a window that is NOT the active window, there is no need to use ShowDialog(IWin32Window).

Answer 3

The IWin32Window parameter is for specifying the owner of the dialog. In this case it's an interface so that you can have non-managed windows (those from a COM object you're using, for example) as the dialog's owner.

I have to disagree with the users here who say that you shouldn't specify an owner. In fact, it's always advisable to specify an owner for a form when possible. While dialogs may not be as important as non-modal forms, getting into the habit of specifying an owner is always a good idea.