How to create a single instance of a winform that is instantiated on a button click event?

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m working on an windows application form(FormA) that has a button,upon button_click event i want another windows form(FormB) instantiated,which is a seperate winform from the main winform (FormA).i want to instantiate the newly instantiated winform(FormB) to have only a single instance,upon button click event it should not create another winform(FormB).is there a way to do this other than using singleton pattern for FormB??Expecting logical approach as answers...Pls give some options..

What I have tried:

expecting efficient approaches..

Posted 23-Feb-17 8:31am

rajkiran.07

Updated 23-Feb-17 9:36am

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[no name] 23-Feb-17 14:37pm

Disable the button that creates the other form. Check the the forms collection to see if there is an existing instance for the form, if there is, do not create a new one. The big question is, what have you tried?

Maciej Los 23-Feb-17 14:55pm

It can't be so easy! :laugh

[no name] 23-Feb-17 15:08pm

Well the easy way is to post a "question" on CP and hope someone does your work for you.

rajkiran.07 23-Feb-17 15:30pm

wasnt expecting C# code for my query, an approach that could point me to a direction would have been helpful..

[no name] 23-Feb-17 15:37pm

And that is exactly what you got.

rajkiran.07 23-Feb-17 15:27pm

i tried it with singleton but the problem is on second attempt on button_click event an exception is thrown as the object is disposed.

rajkiran.07 23-Feb-17 15:32pm

oh,ok i just have to disable the button as long as the obj thats been created on the button_click exist...

rajkiran.07 23-Feb-17 15:36pm

Thank you..and if i create a static field count when an obj is created and compare if its greater than 1 thereby providing a condition under which the obj is created might also work,right?

rajkiran.07 23-Feb-17 15:45pm

Thank you Graeme_Grant & NotPoliticallyCorrect...

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Graeme_Grant · Accepted Answer · 2017-02-23T09:36:00

As NotPoliticallyCorrect mentioned, if the form is open, the button should be disabled.

But to answer your question, the following code does what you ask:

C#

private void ButtonClick(object sender, EventArgs e)
{
    Form form = null;
    if (sender == button1)
    {
        if (Application.OpenForms[nameof(Form1)] == null)
            form = new Form1();
    }
    else // button2
    {
        if (Application.OpenForms[nameof(Form2)] == null)
            form = new Form2();
    }
    if (form != null)
    {
        form.Owner = this;
        form.Show();
    }
}