/// <summary>
/// Handles WM_GETOBJECT message; others are passed to base handler.
/// </summary>
/// <param name="m">Windows message.</param>
/// <remarks>
/// This method enables UI Automation to find the control.
/// In this example, the implementation of IRawElementProvider is in the same class
/// as this method.
/// </remarks>
protected override void WndProc(ref Message m)
{
    const int WM_GETOBJECT = 0x003D;

    if ((m.Msg == WM_GETOBJECT) && (m.LParam.ToInt32() == 
        AutomationInteropProvider.RootObjectId))
    {
        m.Result = AutomationInteropProvider.ReturnRawElementProvider(
                this.Handle, m.WParam, m.LParam, 
                (IRawElementProviderSimple)this);
        return;
    }
    base.WndProc(ref m);
}