How to properly close a form?

Question

I close a form in C#:

loginForm.Close();

However, after that I can open it anymore, the following doesn't work:

loginForm.ShowDialog();

Why is that?

Answer 1

Most likely the underlying handles are disposed not to mention anything that ran in the constructor won't run again. Plus dialogs are a special beast and may have internal flags to indicate modal completion.

It's generally a bad idea to hang onto a window after it has been closed. Perhaps hiding and showing the window is more to your liking?