Only one instance is allowed to run

v2rayN/v2rayN.Desktop/Program.cs

@@ -5,12 +5,44 @@ namespace v2rayN.Desktop;
 
 internal class Program
 {
+    public static EventWaitHandle ProgramStarted;
+
     // Initialization code. Don't use any Avalonia, third-party APIs or any
     // SynchronizationContext-reliant code before AppMain is called: things aren't initialized
     // yet and stuff might break.
     [STAThread]
-    public static void Main(string[] args) => BuildAvaloniaApp()
-        .StartWithClassicDesktopLifetime(args);
+    public static void Main(string[] args)
+    {
+        OnStartup(args);
+
+        BuildAvaloniaApp()
+            .StartWithClassicDesktopLifetime(args);
+    }
+
+    private static void OnStartup(string[]? Args)
+    {
+        if (Utils.IsWindows())
+        {
+            var exePathKey = Utils.GetMd5(Utils.GetExePath());
+            var rebootas = (Args ?? new string[] { }).Any(t => t == Global.RebootAs);
+            ProgramStarted = new EventWaitHandle(false, EventResetMode.AutoReset, exePathKey, out bool bCreatedNew);
+            if (!rebootas && !bCreatedNew)
+            {
+                ProgramStarted.Set();
+                Environment.Exit(0);
+                return;
+            }
+        }
+        else
+        {
+            _ = new Mutex(true, "v2rayN", out var bOnlyOneInstance);
+            if (!bOnlyOneInstance)
+            {
+                Environment.Exit(0);
+                return;
+            }
+        }
+    }
 
     // Avalonia configuration, don't remove; also used by visual designer.
     public static AppBuilder BuildAvaloniaApp()