laatzen/Common/Ui/Common.UI/App.xaml.cs

namespace Common.UI
{
    using Common.UI.Infrastructure;
    using Common.UI.Infrastructure.Contracts;

    using Microsoft.Extensions.DependencyInjection;

    using System;
    using System.Diagnostics;
    using System.Windows;
    using System.Windows.Controls;

    public partial class App : Application
    {
        internal static void InvokeAsync(Action action) 
            => Current.Dispatcher.InvokeAsync(action);

        protected override void OnStartup(StartupEventArgs e)
        {
            if (!this.ShutdownRunningInstance())
            {
                var mainWindow = new MainWindow();
                var args = e.Args;

                if (args?.Length > 0)
                {
                    var source = $"Pages/{args[0]}.xaml";
                    var sourceUri = new Uri(source, UriKind.RelativeOrAbsolute);

                    if (args?.Length > 1)
                    {
                        mainWindow.Navigated += (_, eargs) =>
                        {
                            if (eargs.Content is Page page)
                            {
                                if (int.TryParse($"{args[1]}", out var sharedId))
                                {
                                    page.Tag = sharedId;
                                }
                            }
                        };
                    }

                    mainWindow.NavigationService.Navigate(sourceUri, args[1]);
                }

                AppHost.ConfigureServices(services =>
                {
                    services.AddScoped<INavigation, MainWindow>(_ => mainWindow);
                });

                Current.Exit += (_1, _2) =>
                {
                    ViewModel.ApplicationExit();
                };

                this.MainWindow = mainWindow;
                this.MainWindow.Show();
            }
        }

        private bool ShutdownRunningInstance()
        {
            var currentProcess = Process.GetCurrentProcess();
            var shutdownCalled = false;

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

                    if (windowHandle != IntPtr.Zero)
                    {
                        if (User32DllImports.IsIconic(windowHandle))
                        {
                            User32DllImports.ShowWindow(windowHandle, WindowCommands.Restore);
                        }

                        User32DllImports.SetForegroundWindow(windowHandle);

                        this.Shutdown();

                        shutdownCalled = true;

                        break;
                    }
                }
            }

            return shutdownCalled;
        }
    }
}