Close all open forms except the main menu in C#

Question

Trying to close all forms except for the main menu using

FormCollection formsList = Application.OpenForms;

with a foreach loop and saying,

Answer 1

as the form collection is updating for every iteration. When you close a form, it is removed from the form collection. it's like removing a object from memory while it is using .

Answer 2

Here's an even more concise method that uses the same number of lines as your original method:

Form[] forms = Application.OpenForms.Cast<Form>().ToArray();
foreach (Form thisForm in forms)
{
    if (thisForm.Name != "Menu") thisForm.Close();
}

By using Linq's extension method Cast, you can avoid looping through the collection to build an array.