Class to minimize all forms

Question

How I will Convert this into class which minimize all the childform? When I try to transfer it into class I got error :

The type or namespace name 'MdiChildren' could not be found (are you missing a using directive or an assembly reference?)

public void minimizeAll()
{
   foreach (Form childForm in MdiChildren)
   {
      childForm.WindowState = FormWindowState.Minimized;
   }
}

Answer 1

MdiChildren is not a static property, you need to use an instance of a form. You could pass in a Form as a parameter.

public void minimizeAll(Form parentForm)
{
   foreach (Form childForm in parentForm.MdiChildren)
   {
      childForm.WindowState = FormWindowState.Minimized;
   }
}

Answer 2

You may try using something like this (hardly you have many MDI parent forms):

public static class Minimizer {
  public static void MinimizeMdiChildren() {
    // Enumerate all forms, minimize MDI Children
    foreach (Form form in Application.OpenForms) 
      if (form.IsMdiChild)
        form.WindowState = FormWindowState.Minimized;
  }
}
...
Minimizer.MinimizeMdiChildren();