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原文:WPF：如何实现单实例的应用程序（Single Instance）

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 ProcessProcess thisProc = Process.GetCurrentProcess();// Check how many total processes have the same name as the current oneif (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
{/// <summary>/// App.xaml 的交互逻辑/// </summary>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 IsSingleInstancepublic class SingleInstanceManager : WindowsFormsApplicationBase{SingleInstanceApplication app;public SingleInstanceManager(){this.IsSingleInstance = true;}protected override bool OnStartup(Microsoft.VisualBasic.ApplicationServices.StartupEventArgs e){// First time app is launchedapp = new SingleInstanceApplication();app.Run();return false;}protected override void OnStartupNextInstance(StartupNextInstanceEventArgs eventArgs){// Subsequent launchesbase.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 windowthis.MainWindow.Show();this.MainWindow.Activate();}}
}