private void bt2_Click(object sender, RoutedEventArgs e)
        {
            ChatCline w = new ChatCline();

            w.Owner   = this;
            w.Closed += (sendObj, args) => this.Activate();
            w.Show();
        }
        private void StartWindow(string userName, int left, int top)
        {
            ChatCline w = new ChatCline();

            w.Left     = left;
            w.Top      = top;
            w.UserName = userName;
            w.Owner    = this;
            w.Closed  += (sender, e) => this.Activate();//关闭子窗体时激活父窗体
            w.Show();
        }