Question

I added a couple of forms to a panel. The forms have the properties

form.TopLevel = false;
form.Parent = pnlMain;

Now I want to iterate through all forms in pnlMain and close all forms. To do that I have the following code:

private void CloseForms()
{
    foreach(Form form in pnlMain.Controls.OfType<Form>())
        form.Close();
}

My problem is, that not all forms are closed.

In an example with four open forms: I counted the open forms,

int count = pnlMain.Controls.OfType<Form>().Count();

When I call CloseForms, only two forms are closed. The other two are closed on another call at CloseForms.

How can I close all forms with only one call?

Answer 1

Don’t modify the collection while iterating on it. Try this

foreach(Form form in pnlMain.Controls.OfType<Form>().ToArray())