What event signals that a UserControl is being destroyed?

Solution 1:

I suggest the Control::HandleDestroyed event. It is raised, when the underlying HWnd is destroyed (which usually happens, when the parent form is closed). To handle it in your own UserControl, you should override OnHandleDestroyed.

You have full access to the Control's properties at this moment, because it is not yet disposed of.

Solution 2:

Another solution

    protected override void OnParentChanged(EventArgs e)
    {
        base.OnParentChanged(e);

        if (parentForm != null)
        {
            parentForm.Closing -= parentForm_Closing;
        }
        parentForm = FindForm();

        if (parentForm != null)
            parentForm.Closing += parentForm_Closing;
    }

    void parentForm_Closing(object sender, System.ComponentModel.CancelEventArgs e)
    {
        parentForm.Closing -= parentForm_Closing;
        parentForm = null;
        //closing code
    }