Hi. I'm working with my project right now. In my project, there will be 2 form; I will call form1 and form2. Form 1 call first and then it has button to call form 2. I don't want user open many form2 so I use a private boolean variable. When the button is clicked, it call the function to check the bool variable, if false then show form 1 and set the bool variable to true. And form2 open, and that works to prevent user open many form. But after that, I cannot call it again due to the bool variable that time is true. So i want like when the form closed, it will set the variable to false, but it doesn't work. I use debugger and find out that when I close the form, it will call dispose to erase every resource, so that the instance of the form1 in form2 is deleted. So how can I fix that? All I want is prevent it from open many and open it again when need. I appreciate every answer.