WPF使用扩展屏幕

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Forms;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace ScreenShadow
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            Window1 window = new Window1();
            window.Show();
        }

        private void Button_Click_1(object sender, RoutedEventArgs e)
        {
            Window2 window = new Window2();
            window.Show();
        }
        List<Window> openWindows = new List<Window>();
        private void Button_Click_2(object sender, RoutedEventArgs e)
        {
            openWindows.Clear();
            Screen[] screens = Screen.AllScreens;
            if (screens.Length == )
            {
                lblmsg.Content = "已经投射1个显示器";
            }
            else if (screens.Length == )
            {
                lblmsg.Content = "已经投射2个显示器";
            }
            else if (screens.Length == )
            {
                lblmsg.Content = "已经投射4个显示器";
            }
            else {
                lblmsg.Content = "目前仅支持1，2，4个显示器模式";
            }

            //主屏幕显示
            Screen mainScreen = screens.FirstOrDefault(x=>x.Primary==true);
            //主屏幕显示window1
            Window1 win1 = new Window1();
            win1.WindowState = WindowState.Maximized;
            win1.WindowStartupLocation = WindowStartupLocation.Manual;
            System.Drawing.Rectangle mswa = mainScreen.WorkingArea;
            win1.Left = mswa.Left;
            win1.Top = mswa.Top;
            win1.Width = mswa.Width;
            win1.Height = mswa.Height;
            openWindows.Add(win1);
            win1.Show();

            //其他屏幕显示,这里假设有2个
            var subScreen = (from o in screens where o.Primary == false select o).ToList<Screen>();
            if (subScreen.Count > ) {
                var subscreen1 = subScreen[];
                Window2 win2 = new Window2();
                win1.WindowState = WindowState.Maximized;
                win1.WindowStartupLocation = WindowStartupLocation.Manual;
                System.Drawing.Rectangle mswa2 = subscreen1.WorkingArea;
                win2.Left = mswa2.Left;
                win2.Top = mswa2.Top;
                win2.Width = mswa2.Width;
                win2.Height = mswa2.Height;
                openWindows.Add(win2);
                win2.Show();
            }

        }

        private void BtnClose_Click(object sender, RoutedEventArgs e)
        {
            if (openWindows.Count > ) {
                foreach (var item in openWindows)
                {
                    item.Close();
                }
            }
        }

    }
}