WPF App.xaml.cs常用模板，包括：异常捕获，App只能启动一次

App.xaml.cs中的代码每次都差不多，故特地将其整理出来直接复用：

 using System;
 using System.Configuration;
 using System.Diagnostics;
 using System.Globalization;
 using System.Net;
 using System.Net.Sockets;
 using System.Reflection;
 using System.Runtime.InteropServices;
 using System.Windows;

 namespace WpfDemo
 {
     /// <summary>
     /// App.xaml 的交互逻辑
     /// </summary>
     public partial class App : Application
     {
         private LoginWindow login = new LoginWindow();
         private ILog logger;

         static App()
         {
             log4net.Config.XmlConfigurator.Configure();
         }

         public App()
         {
             logger = LogManager.GetLogger(typeof(this));
         }

         System.Threading.Mutex _mutex;
         protected override void OnStartup(StartupEventArgs e)
         {
             Assembly assembly = Assembly.GetExecutingAssembly();
             string mutexName = string.Format(CultureInfo.InvariantCulture, "Local\\{{{0}}}{{{1}}}", assembly.GetType().GUID, assembly.GetName().Name);
             bool ret = false;
             _mutex = new System.Threading.Mutex(true, mutexName, out ret);
             if (!ret)
             {
                 this.logger.Info("已经运行程序，激活至主窗口.");
                 HandleRunningInstance();
                 Environment.Exit();
                 return;
             }

             base.OnStartup(e);
             this.logger.Info("App startup.");
             this.ShutdownMode = System.Windows.ShutdownMode.OnExplicitShutdown;

             AppDomain.CurrentDomain.UnhandledException += CurrentDomain_UnhandledException;
             this.DispatcherUnhandledException += App_DispatcherUnhandledException;

             this.login.Show();
         }

         void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
         {
             try
             {
                 var exception = e.ExceptionObject as Exception;
                 if (exception != null)
                 {
                     this.logger.FatalFormat("非UI线程全局异常, Message:{0}, Error: {1}", exception.Message, exception.ToString());
                 }
             }
             catch (Exception ex)
             {
                 this.logger.FatalFormat("非UI线程全局异常, Message:{0}, Error: {1}", ex.Message, ex.ToString());
             }
         }

         void App_DispatcherUnhandledException(object sender, System.Windows.Threading.DispatcherUnhandledExceptionEventArgs e)
         {
             try
             {
                 e.Handled = true;
                 this.logger.FatalFormat("UI线程全局异常：Meassage:{0}, Error: {1}", e.Exception.Message, e.Exception.ToString());
             }
             catch (Exception ex)
             {
                 this.logger.FatalFormat("UI线程全局异常：Meassage:{0}, Error: {1}", ex.Message, ex.ToString());
             }
         }

         protected override void OnExit(ExitEventArgs e)
         {
             this.logger.Info("App exit.");

             base.OnExit(e);
         }

         ///<summary>
         /// 该函数设置由不同线程产生的窗口的显示状态
         /// </summary>
         /// <param name="hWnd">窗口句柄</param>
         /// <param name="cmdShow">指定窗口如何显示。查看允许值列表，请查阅ShowWlndow函数的说明部分</param>
         /// <returns>如果函数原来可见，返回值为非零；如果函数原来被隐藏，返回值为零</returns>
         [DllImport("User32.dll")]
         private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);

         /// <summary>
         ///  该函数将创建指定窗口的线程设置到前台，并且激活该窗口。键盘输入转向该窗口，并为用户改各种可视的记号。
         ///  系统给创建前台窗口的线程分配的权限稍高于其他线程。
         /// </summary>
         /// <param name="hWnd">将被激活并被调入前台的窗口句柄</param>
         /// <returns>如果窗口设入了前台，返回值为非零；如果窗口未被设入前台，返回值为零</returns>
         [DllImport("User32.dll")]
         private static extern bool SetForegroundWindow(IntPtr hWnd);

         static Process RunningInstance()
         {
             Process current = Process.GetCurrentProcess();
             Process[] processes = Process.GetProcessesByName(current.ProcessName);
             foreach (Process process in processes)
             {
                 if (process.Id != current.Id)
                 {
                     if (process.MainModule.FileName == current.MainModule.FileName)
                     {
                         return process;
                     }
                 }
             }
             return null;
         }

         private const int SW_NORMAL = ;     //正常弹出窗体
         private const int SW_MAXIMIZE = ;     //最大化弹出窗体

         public static void HandleRunningInstance()
         {
             var instance = RunningInstance();
             if (instance != null)
             {
                 ShowWindowAsync(instance.MainWindowHandle, SW_NORMAL);
                 SetForegroundWindow(instance.MainWindowHandle);
             }
         }
     }
 }