SetForegroundWindow(IntPtr hWnd) not working when application in notification area.

Question

Hi All,
I create a singleton WPF application, when the application is minimize in the notification area. I double click the application's shortcut to call the application. The application cannot show the Main Window in Screen.
Here is the code:
App.cs
public partial class App : Application
[DllImport("user32.dll")]
private static extern bool ShowWindow(IntPtr hwnd, int nCmdShow);
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool SetForegroundWindow(IntPtr hWnd);
private bool _isNewInstance;
public App()
string appName = System.Reflection.Assembly.GetExecutingAssembly().GetName().Name;
Mutex mutex = new Mutex(true, appName, out _isNewInstance);
if (!_isNewInstance)
Application.Current.Shutdown();
Process process = Process.GetProcessesByName(appName).FirstOrDefault();
if (process != null)
ShowWindow(process.MainWindowHandle, 1);
SetForegroundWindow(process.MainWindowHandle);
MainWindow.cs:
private WinForms.NotifyIcon _notifyIcon;
private WinForms.ContextMenu _contextMenu;
private WinForms.MenuItem _openWindow;
private WinForms.MenuItem _closeApp;
private System.ComponentModel.IContainer _iContainer;
private bool _internalClosing;
public MainWindow()
_contextMenu = new WinForms.ContextMenu();
_openWindow = new WinForms.MenuItem() { Text = "Hiden" };
_closeApp = new WinForms.MenuItem() { Text = "Exit"};
_iContainer = new System.ComponentModel.Container();
WinForms.MenuItem[] menuItems = new WinForms.MenuItem[] { _openWindow, _closeApp };
_contextMenu.MenuItems.AddRange(menuItems);
_openWindow.Click += _openWindow_Click;
_closeApp.Click += _closeApp_Click;
_notifyIcon = new WinForms.NotifyIcon(_iContainer);
_notifyIcon.Icon = new System.Drawing.Icon("Todolist.ico");
_notifyIcon.Text = "Todolist";
_notifyIcon.Visible = true;
_notifyIcon.MouseDoubleClick += _notifyIcon_MouseDoubleClick;
_notifyIcon.ContextMenu = _contextMenu;
InitializeComponent();
private void _notifyIcon_MouseDoubleClick(object sender, WinForms.MouseEventArgs e)
this.Show();
ChangeMenuText(false);
private void _openWindow_Click(object sender, EventArgs e)
this.Show();
ChangeMenuText(false);
private void _closeApp_Click(object sender, EventArgs e)
_internalClosing = true;
this.Close();
_internalClosing = false;
private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
if(!_internalClosing)
this.Hide();
e.Cancel = true;
ChangeMenuText(true);
private void ChangeMenuText(bool flag)
_openWindow.Text = flag ? "Show" : "Hiden";
The Screenshot:
Thanks,
The future belongs to those who believe in the beauty of their dreams.

Answer 1

The FindWindow method should get you the handle to the main window. Try to add the following Startup class to your project and set it as Startup object under Project->Properties:
public partial class App : Application
class Startup
[DllImport("user32.dll", EntryPoint = "FindWindow")]
private static extern IntPtr FindWindow(string lp1, string lp2);
[DllImport("user32.dll")]
private static extern bool ShowWindow(IntPtr hwnd, int nCmdShow);
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool SetForegroundWindow(IntPtr hWnd);
[STAThread]
static void Main()
string appName = System.Reflection.Assembly.GetExecutingAssembly().GetName().Name;
using (var mutex = new Mutex(false, appName + "xyz"))
if (!mutex.WaitOne(TimeSpan.FromSeconds(2), false))
IntPtr handle = FindWindow(null, "MainWindow");
if (handle != IntPtr.Zero)
const int SW_SHOW = 5;
const int SW_RESTORE = 9;
ShowWindow(handle, SW_RESTORE);
ShowWindow(handle, SW_SHOW);
SetForegroundWindow(handle);
return;
App app = new App();
app.MainWindow = new MainWindow();
app.MainWindow.Show();
app.Run();
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