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

Since the MdiChildActivate event is fired before the MDI child form is actually closed and therefore there isn't enough information to detect if a MDI child form is actually activated or closed, I chose a different approach to solve the problem.

I found that the ParentChanged event fires on the MDI child form when it is closed.

public class MdiParentForm : Form
{
    // ...

    private Form CreateMdiChildForm()
    {
        var form = new MdiChildForm
        form.ParentChanged += MdiFormParentChangedHandler;
        form.MdiParent = this;
        return form;
    }

    private void MdiFormParentChangedHandler(object sender, EventArgs args)
    {
        var form = sender as Form;
        if (form != null)
        {
            if (form.MdiParent != null)
            {
                // MDI child form will activate
                // ... your code here
            }
            else
            {
                // MDI child form will close
                form.ParentChanged -= MdiFormParentChangedHandler;
                // ... your code here
            }
        }
    }

    // ...
}