CefSharp关闭一个窗口的问题

public class Popup
{

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    private static extern int SetWindowPos(IntPtr hwnd, int hwndInsertAfter, int x, int y, int width, int height, int flags);
    [DllImport("user32.dll")]
    private static extern int GetWindowRect(int hwnd, ref RECT lpRect);
    [DllImport("user32.dll")]
    private static extern IntPtr SetActiveWindow(IntPtr hwnd);

    private struct RECT
    {
        public int Left;
        public int Top;
        public int Right;
        public int Bottom;
    }

    private static void Optimize(Primitives.Popup popup)
    {

        var hwnd = ((HwndSource)PresentationSource.FromVisual(popup.Child)).Handle;

        RECT rect = default(RECT);
        int r = GetWindowRect((int)hwnd, ref rect);
        if (r == 0) return;

        double Width = !double.IsNaN(popup.Width) && popup.Width > 0 ? popup.Width : popup.ActualWidth;
        double Height = !double.IsNaN(popup.Height) && popup.Height > 0 ? popup.Height : popup.ActualHeight;

        SetWindowPos(hwnd, -1, rect.Left, rect.Top, (int)Width, (int)Height, 0);

    }

    private static List<int> instances = new List<int>();

    public static void AutoRender()
    {
        EventManager.RegisterClassHandler(typeof(Primitives.Popup), Primitives.Popup.PreviewGotKeyboardFocusEvent, new KeyboardFocusChangedEventHandler(OnPreviewGotKeyboardFocus), true);
    }

    private static void OnPreviewGotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
    {

        try
        {

            var textBox = e.NewFocus as TextBoxBase;
            if (textBox == null) return;

            IntPtr hwnd = ((HwndSource)PresentationSource.FromVisual(textBox)).Handle;
            if (hwnd != IntPtr.Zero && !instances.Contains(hwnd.ToInt32()))
            {
                instances.Add(hwnd.ToInt32());
                SetActiveWindow(hwnd);
            }

        }
        catch (Exception) { }
            
    }

}