好吧，这是我将WPF与Windows Forms进行比较的系列文章的第四篇，讨论一下如何实现单实例(single instance)
先来看第一种最简单粗暴的做法:
检测进程名,如果名称一样,则表示程序已经启动了,就不再启动.
protected override void OnStartup(StartupEventArgs e) { // Get Reference to the current Process Process thisProc = Process.GetCurrentProcess(); // Check how many total processes have the same name as the current one if (Process.GetProcessesByName(thisProc.ProcessName).Length > 1) { // If ther is more than one, than it is already running. MessageBox.Show("Application is already running."); Application.Current.Shutdown(); return; } base.OnStartup(e); }很简单,不是吗?但简单有什么错呢? 它很实用. [注意]这个代码如果在visual studio中调试则无效，因为visual studio调试用的进程是加了一个vshost的后缀的。
第二种方案我觉得应该还是可以用来实现嘛，看看下面的代码
using System;using System.Collections.Generic;using System.Configuration;using System.Data;using System.Linq;using System.Windows;using System.Diagnostics;using System.Threading;namespace WpfApplication1{ /// /// App.xaml 的交互逻辑 /// public partial class App : Application { protected override void OnStartup(StartupEventArgs e) { bool createNew; Mutex mutex = new Mutex(true, "MyApplication", out createNew); if (createNew) base.OnStartup(e); else { MessageBox.Show("程序已经启动了"); Application.Current.Shutdown(); } } }} 这一种做法的结果与第一种很类似，或者说没有任何区别。
看起来解决问题了，但仍然不是很理想的。最好的情况是，当用户开启第二个实例的时候，如果第一个实例没有处于活动状态，则应该激活它。
我们很自然还是联想到了原先在Windows Forms时代的WindowsFormsApplicationBase，那里面做这个事情太简单了。
首先，添加Microsoft.VisualBasic的引用
namespace WpfApplication1{ public class EntryPoint { [STAThread] public static void Main(string[] args) { SingleInstanceManager manager = new SingleInstanceManager(); manager.Run(args); } } // Using VB bits to detect single instances and process accordingly: // * OnStartup is fired when the first instance loads // * OnStartupNextInstance is fired when the application is re-run again // NOTE: it is redirected to this instance thanks to IsSingleInstance public class SingleInstanceManager : WindowsFormsApplicationBase { SingleInstanceApplication app; public SingleInstanceManager() { this.IsSingleInstance = true; } protected override bool OnStartup(Microsoft.VisualBasic.ApplicationServices.StartupEventArgs e) { // First time app is launched app = new SingleInstanceApplication(); app.Run(); return false; } protected override void OnStartupNextInstance(StartupNextInstanceEventArgs eventArgs) { // Subsequent launches base.OnStartupNextInstance(eventArgs); app.Activate(); } } public class SingleInstanceApplication : Application { protected override void OnStartup(System.Windows.StartupEventArgs e) { base.OnStartup(e); // Create and show the application's main window //MainWindow window = new MainWindow(); Window1 window = new Window1(); window.Show(); } public void Activate() { // Reactivate application's main window this.MainWindow.Show(); this.MainWindow.Activate(); } }}