通过App.xaml理解wpf中的Application类

<Application x:Class="ApplicationLifeCycle.App"
       xmlns="Http://schemas.microsoft.com/winfx/2006/xaml/presentation"
       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
       xmlns:local="clr-namespace:ApplicationLifeCycle"
       StartupUri="MainWindow.xaml"> 
  <Application.Resources>
     
  </Application.Resources>
</Application>

using System.Text;
using System.windows;

namespace ApplicationLifeCycle
{
  /// <summary>
  /// App.xaml 的交互逻辑
  /// </summary>
  public partial class App : Application
  { 

    protected override void OnStartup(StartupEventArgs e)
    {
      base.OnStartup(e); 
      StringBuilder sb = new StringBuilder();
      foreach (var item in e.Args)
      {
        sb.Append(item);
      } 
      MessageBox.Show($"args length as {e.Args.Length},args content as {sb.ToString()}");
     
    }
  }
}

private bool _unsavedData = false;
    public bool UnsavedData
    {
      get { return _unsavedData; }
      set
      {
        _unsavedData = value;
      }
    }

    protected override void OnSessionEnding(SessionEndinGCancelEventArgs e)
    {
      base.OnSessionEnding(e);
      //假设某些线程未完成保存，把UnsaveData设置为True
      UnsavedData = true;
      if (UnsavedData)
      {
        e.Cancel = true;
        MessageBox.Show($"我们的数据尚未保存完毕，{e.ReasonSessionEnding} 将丢失数据。");
      }
    }

private void GetCurrentWindowListButton_Click(object sender, RoutedEventArgs e)
    {
      Window mainWindow = Application.Current.MainWindow;
      foreach (var item in Application.Current.Windows)
      {
        var title = ((Window)item).Title;
      }

    }