下面是我使用的一个轻量级解决方案，它允许应用程序将一个已经存在的窗口带到前台，而无需求助于自定义窗口消息或盲目地搜索进程名。

[DllImport("user32.dll")]
static extern bool SetForegroundWindow(IntPtr hWnd);

static readonly string guid = "<Application Guid>";

static void Main()
{
    Mutex mutex = null;
    if (!CreateMutex(out mutex))
        return;

    // Application startup code.

    Environment.SetEnvironmentVariable(guid, null, EnvironmentVariableTarget.User);
}

static bool CreateMutex(out Mutex mutex)
{
    bool createdNew = false;
    mutex = new Mutex(false, guid, out createdNew);

    if (createdNew)
    {
        Process process = Process.GetCurrentProcess();
        string value = process.Id.ToString();

        Environment.SetEnvironmentVariable(guid, value, EnvironmentVariableTarget.User);
    }
    else
    {
        string value = Environment.GetEnvironmentVariable(guid, EnvironmentVariableTarget.User);
        Process process = null;
        int processId = -1;

        if (int.TryParse(value, out processId))
            process = Process.GetProcessById(processId);

        if (process == null || !SetForegroundWindow(process.MainWindowHandle))
            MessageBox.Show("Unable to start application. An instance of this application is already running.");
    }

    return createdNew;
}

编辑:你也可以静态地存储和初始化互斥量和createdNew，但是一旦你完成了它，你需要显式地释放/释放互斥量。就我个人而言，我更喜欢将互斥锁保持在本地，因为即使应用程序在未到达Main结束时就关闭，它也会被自动销毁。

看起来有一个很好的方法来处理这个问题:

WPF单实例应用程序

这提供了一个类，您可以添加它来管理所有互斥量和消息传递的cruff，从而将实现简化到非常简单的程度。

基于Matt Davis的答案，为方便起见包装成一个类。

public static class SingleAppInstanceChecker
{
    /// <summary>
    /// Arbitrary unique string
    /// </summary>
    private static Mutex _mutex = new Mutex(true, "0d12ad74-026f-40c3-bdae-e178ddee8602");

    public static bool IsNotRunning()
    {
        return _mutex.WaitOne(TimeSpan.Zero, true);
    }
}

使用示例:

private void Application_Startup(object sender, StartupEventArgs e)
{
    if (!SingleAppInstanceChecker.IsNotRunning())
    {
        MessageBox.Show("Application is already running.");

        // Exit application using:
        // Environment.Exit(1);
        // Application.Current.Shutdown();
        // Etc...

        return;
    }
    
    // Allow startup and continue with normal processing
    // ...
}

我喜欢一个解决方案，以允许多个实例，如果exe是从其他路径调用。我修改了CharithJ溶液方法一:

   static class Program {
    [DllImport("user32.dll")]
    private static extern bool ShowWindow(IntPtr hWnd, Int32 nCmdShow);
    [DllImport("User32.dll")]
    public static extern Int32 SetForegroundWindow(IntPtr hWnd);
    [STAThread]
    static void Main() {
        Process currentProcess = Process.GetCurrentProcess();
        foreach (var process in Process.GetProcesses()) {
            try {
                if ((process.Id != currentProcess.Id) && 
                    (process.ProcessName == currentProcess.ProcessName) &&
                    (process.MainModule.FileName == currentProcess.MainModule.FileName)) {
                    ShowWindow(process.MainWindowHandle, 5); // const int SW_SHOW = 5; //Activates the window and displays it in its current size and position. 
                    SetForegroundWindow(process.MainWindowHandle);
                    return;
                }
            } catch (Exception ex) {
                //ignore Exception "Access denied "
            }
        }

        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new Form1());
    }
}

永远不要使用命名互斥来实现单实例应用程序(至少在生产代码中不要这样做)。恶意代码可以很容易地DoS(拒绝服务)你的屁股…

一个节省时间的c# Winforms解决方案…

Program.cs:

using System;
using System.Windows.Forms;
// needs reference to Microsoft.VisualBasic
using Microsoft.VisualBasic.ApplicationServices;  

namespace YourNamespace
{
    public class SingleInstanceController : WindowsFormsApplicationBase
    {
        public SingleInstanceController()
        {
            this.IsSingleInstance = true;
        }

        protected override void OnStartupNextInstance(StartupNextInstanceEventArgs e)
        {
            e.BringToForeground = true;
            base.OnStartupNextInstance(e);
        }

        protected override void OnCreateMainForm()
        {
            this.MainForm = new Form1();
        }
    }

    static class Program
    {
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            string[] args = Environment.GetCommandLineArgs();
            SingleInstanceController controller = new SingleInstanceController();
            controller.Run(args);
        }
    }
}