App.xaml.cs

using System;
using System.Globalization;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;

namespace ExchangeRateServer
{
	public partial class App : Application
	{
		internal static bool flag_log;
		internal static bool flag_debug;

		private static readonly CultureInfo Culture = new("en-US");

		private const string UniqueEventName = "{3596C906-E192-47BD-B890-B79591261EDD}";
		private EventWaitHandle eventWaitHandle;

		public App()
		{
			ShutdownMode = ShutdownMode.OnExplicitShutdown;
			SingleInstanceWatcher();
			CultureInfo.DefaultThreadCurrentCulture = Culture;
		}

		private void SingleInstanceWatcher()
		{
			try
			{
				eventWaitHandle = EventWaitHandle.OpenExisting(UniqueEventName);
				_ = eventWaitHandle.Set();
				Shutdown();
			}
			catch (WaitHandleCannotBeOpenedException)
			{
				eventWaitHandle = new EventWaitHandle(false, EventResetMode.AutoReset, UniqueEventName);
			}

			new Task(() =>
			{
				while (eventWaitHandle.WaitOne())
				{
					_ = Current.Dispatcher.BeginInvoke((Action)(() =>
					  {
						  if (!Current.MainWindow.Equals(null))
						  {
							  var mw = Current.MainWindow;

							  if (mw.WindowState == WindowState.Minimized || mw.Visibility != Visibility.Visible)
							  {
								  mw.Show();
								  mw.WindowState = WindowState.Normal;
							  }

							  _ = mw.Activate();
							  mw.Topmost = true;
							  mw.Topmost = false;
							  _ = mw.Focus();
						  }
					  }));
				}
			})
			.Start();
		}

		protected override void OnStartup(StartupEventArgs e)
		{
			ShutdownMode = ShutdownMode.OnMainWindowClose;

			Current.DispatcherUnhandledException += (x, ex) =>
			{
				if (!Directory.Exists("log"))
				{
					_ = Directory.CreateDirectory("log");
				};

				File.AppendAllText(@"log\crash.txt", "Unknown Application Wide Exception: " + ex.Exception.Message + "\n" + ex.Exception.StackTrace);
			};

			for (var i = 0; i != e.Args.Length; ++i)
			{
				if (e.Args[i] == "/log")
				{
					flag_log = true;
				}

				if (e.Args[i] == "/debug")
				{
					flag_debug = true;
				}
			}

			base.OnStartup(e);
		}
	}
}