How do you stop multiple forms from opening when you click a button more than once-CodePudding

private void Button_Click_1(object sender, EventArgs e)
{
    Form2.form = new Form2();
    form.Show();
}

When you click the button twice, 2 forms pop up, how do I make it so when you click the button twice it gets rid of the form already open and opens up the form alone.

Example of what I want:

Click the button once, makes Form2 open
Click the button twice, makes the original Form2 close, and open another Form2 alone.

What actually happens:

Click the button once, makes Form2 open
Click the button twice, the original Form2 is still open and it opens another Form2

CodePudding user response：

You'll just need to loop through each of the open forms and check the name of the form to see if it is the same. Try the following:

foreach (Form frm in Application.OpenForms)
{
    if (frm.Name == "form2") //Whatever the actual name of your form is
    {
        frm.Close();
    }
}

Form2 form2 = new Form2();
form2.Show();

CodePudding user response：

You can build a simple method that verifies whether an instance of a Form of a Type you supply exists: if it does, closes the current instance and generates a new one of the same Type:

private void OpenNew<T>() where T : Form, new()
{
    var instance = Application.OpenForms.OfType<T>().FirstOrDefault();
    if (instance != null) instance.Close();
    new T().Show();
}

Assuming that you generate an instance of this Type only using a specific Button.

If more than one instance of that Type can exist, for some reason, loop the collection returned by Application.OpenForms.OfType<T>() ( .ToArray() to avoid... well, try it without it ):

private void OpenNew<T>() where T : Form, new()
{
    foreach (var instance in Application.OpenForms.OfType<T>().ToArray()) {
        instance.Close();
    }
    new T().Show();
}

=> you can loop the collection also as:

Application.OpenForms.OfType<T>().ToList().ForEach(f => f.Close());

You can call either of these methods (use the one you prefer in your context: you may need to do something else before showing a new, always single, instance or a new one of the many) as, e.g., :

OpenNew<Form2>();