CODEWITHSUNDEEP
c#winformsforms
Dinesh
Dinesh

Reputation: 2066

How to prevent the Form from opening Multiple Times

I have a application in which i have several forms. In that forms, I have a System Settings form. I have to open this form from the menu as well as a shortcut created on the desktop.

I am able to open the form from 2 places individually. But the problem is, It's opening two separate instance of the same form. it means, first, i have clicked on menu to open the form.Now my Form instance is created and it is displayed on the screen. But whenever i click on my desktop icon, It's creating another instance of the same form instead of displaying the same form. . So it means it's displaying two instances of the same form.

But i have display one form only. I have tried and googled in the net also. I didn't find any information.

Can anybody please help me to fix this issue. Any kind of suggestion will be really helpful to me.

Upvotes: 2

Views: 3772

Answers (6)

James C
James C

Reputation: 514

Sounds like you need a modified version of the Singleton design pattern. Try having a public static method within the class that internally calls the constructor for the form. Then as someone suggested use a counter variable to keep track of how may times that static method is called thus giving you a metric you can use to ensure only the desired number if instance are created.

Upvotes: 0

Dinesh
Dinesh

Reputation: 2066

I have used semaphor concept to control this. Whenever the form is opened i am writing an entry into registry. Once the form is closed i am removing this entry.

So, whenever i try to open the form, it will check the registry entry. Based on that it will open the form.

Upvotes: 0

Oliver
Oliver

Reputation: 45101

You need a single instance. This construct is already available within the .Net framework. Just check out this post from Hanselman.

Note: I know that the namespace of this class is VisualBasic. But that shouldn't hinder you to use it in your C# application. It's just the name of a namespace. It doesn't meant anything about its functionality. (Microsoft had it better named Foo. In that case it would be much more popular.)

Upvotes: 3

Greg Sexton
Greg Sexton

Reputation: 9279

To throw in one more link, this post seems to cover (my understanding of) what you are trying to do.

http://dotnetperls.com/single-instance-windows-form

Upvotes: 0

m0s
m0s

Reputation: 4280

You have to implement some kind of locking mechanism to allow only one instance of your program running. I guess your System Settings program could check if other instances are running on computer on program launch, if so terminate, otherwise start a new instance.

Upvotes: 0

Dennis
Dennis

Reputation: 2142

Sounds to me, that you need a mutex to control that only one application instance is running at a given time.

See http://iridescence.no/post/CreatingaSingleInstanceApplicationinC.aspx for further details

Upvotes: 2

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