我在这里找不到一个简单的解决方案，所以我希望有人会喜欢这个:

更新2018-09-20

把这段代码放在Program.cs中:

using System.Diagnostics;

static void Main()
{
    Process thisProcess = Process.GetCurrentProcess();
    Process[] allProcesses = Process.GetProcessesByName(thisProcess.ProcessName);
    if (allProcesses.Length > 1)
    {
        // Don't put a MessageBox in here because the user could spam this MessageBox.
        return;
    }

    // Optional code. If you don't want that someone runs your ".exe" with a different name:

    string exeName = AppDomain.CurrentDomain.FriendlyName;
    // in debug mode, don't forget that you don't use your normal .exe name.
    // Debug uses the .vshost.exe.
    if (exeName != "the name of your executable.exe") 
    {
        // You can add a MessageBox here if you want.
        // To point out to users that the name got changed and maybe what the name should be or something like that^^ 
        MessageBox.Show("The executable name should be \"the name of your executable.exe\"", 
            "Wrong executable name", MessageBoxButtons.OK, MessageBoxIcon.Error);
        return;
    }

    // Following code is default code:
    Application.EnableVisualStyles();
    Application.SetCompatibleTextRenderingDefault(false);
    Application.Run(new MainForm());
}

[我在下面提供了控制台和wpf应用程序的示例代码。]

在创建命名的Mutex实例后，只需检查createdNew变量的值(示例如下!)。

布尔值createdNew将返回false:

如果命名为“YourApplicationNameHere”的互斥锁实例已经存在 在系统某处创建

布尔值createdNew将返回true:

如果这是第一个名为“YourApplicationNameHere”的互斥锁 系统。

控制台应用程序-示例:

static Mutex m = null;

static void Main(string[] args)
{
    const string mutexName = "YourApplicationNameHere";
    bool createdNew = false;

    try
    {
        // Initializes a new instance of the Mutex class with a Boolean value that indicates 
        // whether the calling thread should have initial ownership of the mutex, a string that is the name of the mutex, 
        // and a Boolean value that, when the method returns, indicates whether the calling thread was granted initial ownership of the mutex.

        using (m = new Mutex(true, mutexName, out createdNew))
        {
            if (!createdNew)
            {
                Console.WriteLine("instance is alreday running... shutting down !!!");
                Console.Read();
                return; // Exit the application
            }

            // Run your windows forms app here
            Console.WriteLine("Single instance app is running!");
            Console.ReadLine();
        }


    }
    catch (Exception ex)
    {

        Console.WriteLine(ex.Message);
        Console.ReadLine();
    }
}

WPF-Example:

public partial class App : Application
{
static Mutex m = null;

protected override void OnStartup(StartupEventArgs e)
{

    const string mutexName = "YourApplicationNameHere";
    bool createdNew = false;

    try
    {
        // Initializes a new instance of the Mutex class with a Boolean value that indicates 
        // whether the calling thread should have initial ownership of the mutex, a string that is the name of the mutex, 
        // and a Boolean value that, when the method returns, indicates whether the calling thread was granted initial ownership of the mutex.

        m = new Mutex(true, mutexName, out createdNew);

        if (!createdNew)
        {
            Current.Shutdown(); // Exit the application
        }

    }
    catch (Exception)
    {
        throw;
    }

    base.OnStartup(e);
}


protected override void OnExit(ExitEventArgs e)
{
    if (m != null)
    {
        m.Dispose();
    }
    base.OnExit(e);
}
}

通常，这是我用于单实例Windows窗体应用程序的代码:

[STAThread]
public static void Main()
{
    String assemblyName = Assembly.GetExecutingAssembly().GetName().Name;

    using (Mutex mutex = new Mutex(false, assemblyName))
    {
        if (!mutex.WaitOne(0, false))
        {
            Boolean shownProcess = false;
            Process currentProcess = Process.GetCurrentProcess();

            foreach (Process process in Process.GetProcessesByName(currentProcess.ProcessName))
            {
                if (!process.Id.Equals(currentProcess.Id) && process.MainModule.FileName.Equals(currentProcess.MainModule.FileName) && !process.MainWindowHandle.Equals(IntPtr.Zero))
                {
                    IntPtr windowHandle = process.MainWindowHandle;

                    if (NativeMethods.IsIconic(windowHandle))
                        NativeMethods.ShowWindow(windowHandle, ShowWindowCommand.Restore);

                    NativeMethods.SetForegroundWindow(windowHandle);

                    shownProcess = true;
                }
            }

            if (!shownProcess)
                MessageBox.Show(String.Format(CultureInfo.CurrentCulture, "An instance of {0} is already running!", assemblyName), assemblyName, MessageBoxButtons.OK, MessageBoxIcon.Asterisk, MessageBoxDefaultButton.Button1, (MessageBoxOptions)0);
        }
        else
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form());
        }
    }
}

本地组件的位置:

[DllImport("User32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
internal static extern Boolean IsIconic([In] IntPtr windowHandle);

[DllImport("User32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
internal static extern Boolean SetForegroundWindow([In] IntPtr windowHandle);

[DllImport("User32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
internal static extern Boolean ShowWindow([In] IntPtr windowHandle, [In] ShowWindowCommand command);

public enum ShowWindowCommand : int
{
    Hide                   = 0x0,
    ShowNormal             = 0x1,
    ShowMinimized          = 0x2,
    ShowMaximized          = 0x3,
    ShowNormalNotActive    = 0x4,
    Minimize               = 0x6,
    ShowMinimizedNotActive = 0x7,
    ShowCurrentNotActive   = 0x8,
    Restore                = 0x9,
    ShowDefault            = 0xA,
    ForceMinimize          = 0xB
}

这就是我最终处理这个问题的方式。注意，调试代码仍然在那里进行测试。这段代码在App.xaml.cs文件的OnStartup中。(WPF)

        // Process already running ? 
        if (Process.GetProcessesByName(Process.GetCurrentProcess().ProcessName).Length > 1)
        {

            // Show your error message
            MessageBox.Show("xxx is already running.  \r\n\r\nIf the original process is hung up you may need to restart your computer, or kill the current xxx process using the task manager.", "xxx is already running!", MessageBoxButton.OK, MessageBoxImage.Exclamation);

            // This process 
            Process currentProcess = Process.GetCurrentProcess();

            // Get all processes running on the local computer.
            Process[] localAll = Process.GetProcessesByName(Process.GetCurrentProcess().ProcessName);

            // ID of this process... 
            int temp = currentProcess.Id;
            MessageBox.Show("This Process ID:  " + temp.ToString());

            for (int i = 0; i < localAll.Length; i++)
            {
                // Find the other process 
                if (localAll[i].Id != currentProcess.Id)
                {
                    MessageBox.Show("Original Process ID (Switching to):  " + localAll[i].Id.ToString());

                    // Switch to it... 
                    SetForegroundWindow(localAll[i].MainWindowHandle);

                }
            }

            Application.Current.Shutdown();

        }

这可能有我还没有发现的问题。如果我遇到了，我会更新我的答案。

但是不使用互斥，简单的回答:

System.Diagnostics;    
...
string thisprocessname = Process.GetCurrentProcess().ProcessName;

if (Process.GetProcesses().Count(p => p.ProcessName == thisprocessname) > 1)
                return;

把它放在Program.Main()中。 例子:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Diagnostics;

namespace Sample
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            //simple add Diagnostics namespace, and these 3 lines below 
            string thisprocessname = Process.GetCurrentProcess().ProcessName;
            if (Process.GetProcesses().Count(p => p.ProcessName == thisprocessname) > 1)
                return;

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

您可以添加MessageBox。在if语句中显示并输入“应用程序已运行”。 这可能对某些人有帮助。

我在解决方案中使用互斥来防止多个实例。

static Mutex mutex = null;
//A string that is the name of the mutex
string mutexName = @"Global\test";
//Prevent Multiple Instances of Application
bool onlyInstance = false;
mutex = new Mutex(true, mutexName, out onlyInstance);

if (!onlyInstance)
{
  MessageBox.Show("You are already running this application in your system.", "Already Running..", MessageBoxButton.OK);
  Application.Current.Shutdown();
}