MDI Form detecting with a child form is added or removed

Question

Is there an event I can use to tell if a child form has been added or removed from the MDI parent?

Answer 1

Wire up the MdiChildActivate event and keep a list of recognized children. When a new form is activated, also wire up the FormClosed event.

private List
 ChildFormList = new List();

private void MyForm_MdiChildActivate(object sender, EventArgs e)
{
    Form f = this.ActiveMdiChild;

    if (f == null)
    {
        //the last child form was just closed
        return;
    }

    if (!ChildFormList.Contains(f))
    {
        //a new child form was created
        ChildFormList.Add(f);
        f.FormClosed += new FormClosedEventHandler(ChildFormClosed);
    }
    else
    {
        //activated existing form
    }
}

private void ChildFormClosed(object sender, FormClosedEventArgs e)
{
    //a child form was closed
    Form f = (Form)sender;
    ChildFormList.Remove(f);
}