Visible = false;
or
this.Hide();
Why thouse cleses "releases" my Window?
I want to hide and restore , not to release ...
Which method to use?
I guess that in your Main method, you have something like that:
Application.Run(new Form1());
where Form1 is the name of your main form. In this case, when your main
form closes or is hiden, the message loop started by Application.Run is
stopped and your application closes.
To avoid this behaviour, make your message loop independent from your form.
Replace the above line by:
Form1 f = new Form1();
f.Show();
Application.Run();
Now you can hide and show your form without the message loop stopping
itself automatically. Keep in mind however that it is now your task to stop
the message loop with Application.Exit() as the message loop is not linked
with your main form anymore. So handle the Closing event of your main form
and call Application.Exit() there.