1、添加用于启动的类Program.cs，需要一个静态的Main函数入口。

using System;
using System.Windows;
using System.Windows.Controls;

棕色部分实现窗口的位置固定和跟随。

public class Program
    {
        private static Application _MainApplication;

        internal static Application MainApplication
        {
            get { return _MainApplication ?? (_MainApplication = new Application()); }
        }

        [STAThread]
        public static void Main(string[] args)
        {
            var MainWin = new Window();
            var FollowWin = new Window();
            //拉姆达表达式
            MainWin.Loaded +=
                (s, e) =>
                {
                    FollowWin.WindowStartupLocation = WindowStartupLocation.Manual;
                    FollowWin.Left = MainWin.Left + MainWin.Width;
                    FollowWin.Top = MainWin.Top;
                    FollowWin.Show();
                };
            //当窗口位置更改时发生
            MainWin.LocationChanged +=
                (s, e) =>
                {
                    FollowWin.Left = MainWin.Left + MainWin.Width;
                    FollowWin.Top = MainWin.Top;
                };
            MainApplication.ShutdownMode = ShutdownMode.OnExplicitShutdown;
            MainApplication.Run(touch);
        }
    }

2、设置类库项目的输出类型为“Windows应用程序”：

3、设置启动对象为第一步中创建的Program

4、运行即可。