Windows Form Problem [Singleton]

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C#

WinForms

I'm wanting to check to see how many times a particular form is opened in my project, so that only one form is open.

Posted 27-Jan-11 2:16am

NBajaj

Updated 27-Jan-11 3:47am

Andrew Rissing

v2

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4 solutions

Solution 1

Why not just create your form as a member variable, and thus you'll only ever be able to show one ? If you want to track how many, just put a static variable in the form that gets incremented. The lack of deterministic destruction means it's most reliable to make it go up and down by hand, although there's probably an event you can hook in to to do it for you, still, such as when the forms visible status changes to not visible.

Posted 27-Jan-11 2:25am

Christian Graus

Solution 2

Adding to CG's response
---------------------------

One popular approach is to hook the Closed event of the form in the parent form, so that when the child form's closed, the member variable can be set to null. Thus if the member variable is null, it means the form needs to be recreated and reshown, else it means the form's already visible and probably just needs to be focused/activated.

Posted 27-Jan-11 4:00am

Nish Nishant

v2

Comments

Espen Harlinn 27-Jan-11 17:26pm

5+ either that or just hide the form on close, and reuse the instance

Nish Nishant 27-Jan-11 18:50pm

Yeah, that'd work too.

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SilimSayo · Accepted Answer · 2011-01-27T06:28:00

Solution 3

See this link about singletons. I have used this pattern in the past to ensure I only have one instance of a form.

http://msdn.microsoft.com/en-us/library/ff650316.aspx[^]

Posted 27-Jan-11 6:28am

SilimSayo

Manfred Rudolf Bihy · Accepted Answer · 2011-01-27T11:00:00

If you're looking for a solution that will make sure that only one instance of a form is ever opened please have a look at my answer to this question (Answer 2): How to open only one instance of class not more than that?[^]
It handles a case were only one instance of a form is ever to be opened while the application is running.

Hope that helps you!