Cosing all forms in an application

Cosing all forms in an application seems like it would be a simple task of using a foreach loop in the Application.OpenForms collection, such as:

foreach (Form form in Application.OpenForms)
{
form.Close();


But there are two problems.
First, the code above will throw an exception because the OpenForms collection changes each time you close a form, and so the enumerator in your foreach loop becomes invalid when you close a form. Instead, you need to get an array of all open forms, then loop through the array:
static public void CloseAllForms()
{
// get array because collection changes as we close forms
Form[] forms = OpenForms;

// close every open form
foreach (Form form in forms)
{
CloseForm( form );
}
}


Second, it’s quite possible that your application opened one or more forms in a separate thread. If so, then trying to close a form from your main thread will throw an exception. So you need to close your forms in a thread-safe manner:

delegate void CloseMethod( Form form );
static private void CloseForm( Form form )
{
if (!form.IsDisposed)
{
if (form.InvokeRequired)
{
CloseMethod method = new CloseMethod( CloseForm );
form.Invoke( method, new object[] { form } );
}
else
{
form.Close();
}
}
}