你曾经是否遇到过只准打开一个 WPF 应用程序实例这样的需求，如果有这样的需求场景，下面的方法应该可以满足你的需求：
public partial class App : Application
{
private EventWaitHandle AppEventWait;
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
StartSingleInstanceApp();
}
/// <summary>
/// 开启单实例应用
/// </summary>
private void StartSingleInstanceApp()
{
String mutexName = "f7eeb38e-3ede-4fdb-8891-b285bff816e8";
AppEventWait = new EventWaitHandle(false, EventResetMode.AutoReset, mutexName, out var isNewInstance);
if (!isNewInstance)
{
AppEventWait.Set();
App.Current.Shutdown();
return;
}
AppListenTask();
}
private void AppListenTask()
{
Task.Run(() =>
{
AppEventWait.Reset();
AppEventWait.WaitOne();
App.Current.Dispatcher.BeginInvoke(new Action(() =>
{
App.Current.MainWindow.Activate();
App.Current.MainWindow.WindowState = WindowState.Maximized;
}));
AppListenTask();
});
}
}
很长一段时间，我一直用上面的方法实现 WPF 单实例应用，后来发现还有更好更优雅的方式：
public partial class App : Application
{
private const String MUTEX_NAME = "f7eeb38e-3ede-4fdb-8891-b285bff816e8";
private EventWaitHandle? _eventEaitHandle;
private const Int32 SW_SHOW = 5;
[DllImport("User32.dll")]
private static extern Boolean ShowWindowAsync(IntPtr hWnd, Int32 cmdShow);
[DllImport("User32.dll")]
private static extern Boolean SetForegroundWindow(IntPtr hWnd);
[DllImport("user32.dll")]
private static extern void SwitchToThisWindow(IntPtr hWnd, Boolean fUnknown);
/// <summary>
/// 开启单实例应用
/// </summary>
protected override void OnStartup(StartupEventArgs e)
{
App.Current.ShutdownMode = ShutdownMode.OnMainWindowClose;
this._eventEaitHandle = new EventWaitHandle(false, EventResetMode.AutoReset, MUTEX_NAME, out var newInstance);
if (!newInstance)
{
var currProcess = Process.GetCurrentProcess();
var processes = Process.GetProcessesByName(currProcess.ProcessName);
if (processes is not null)
{
var lastProcess = processes.FirstOrDefault((t) => { return t.Id != currProcess.Id; });
if (lastProcess is not null)
{
ShowWindowAsync(lastProcess.MainWindowHandle, SW_SHOW);
SetForegroundWindow(lastProcess.MainWindowHandle);
SwitchToThisWindow(lastProcess.MainWindowHandle, true);
App.Current.Shutdown();
Environment.Exit(-1);
return;
}
}
}
}
}