Window Management

Window Management

The Dapplo.Windows package provides the InteropWindow class for querying, enumerating, and manipulating windows through native Windows APIs.

Installation

Install-Package Dapplo.Windows

Getting Window Information

From Window Handle

using Dapplo.Windows.Desktop;
using Dapplo.Windows.User32;

// Get the foreground window
IntPtr handle = User32Api.GetForegroundWindow();
IInteropWindow window = InteropWindow.FromHandle(handle);

// Populate all window properties
window.Fill();

Console.WriteLine($"Title:    {window.Caption}");
Console.WriteLine($"Class:    {window.Classname}");
Console.WriteLine($"PID:      {window.ProcessId}");
Console.WriteLine($"Bounds:   {window.Bounds}");

Selective Property Loading

For better performance, load only the properties you need:

using Dapplo.Windows.Desktop;

var window = InteropWindow.FromHandle(handle);
window.Fill(InteropWindowRetrieveSettings.Caption |
            InteropWindowRetrieveSettings.Info);

Console.WriteLine($"{window.Caption} at {window.Bounds}");

Enumerating Windows

All Top-Level Windows

using Dapplo.Windows.Desktop;

var windows = InteropWindowQuery.GetTopLevelWindows();
foreach (var window in windows)
{
    Console.WriteLine($"{window.Caption} ({window.Classname})");
}

Filtered Windows

using Dapplo.Windows.Desktop;
using System.Linq;

// Visible windows only
var visible = InteropWindowQuery.GetTopLevelWindows()
    .Where(w => w.IsVisible())
    .ToList();

// By process executable name
var notepadWindows = InteropWindowQuery.GetTopLevelWindows()
    .Where(w => w.GetProcessPath()?.Contains("notepad.exe") ?? false)
    .ToList();

// By window class
var explorerWindows = InteropWindowQuery.GetTopLevelWindows()
    .Where(w => w.GetClassname() == "CabinetWClass")
    .ToList();

Child Windows

using Dapplo.Windows.Desktop;

var parent = InteropWindow.FromHandle(handle);
parent.Fill(InteropWindowRetrieveSettings.Children);

foreach (var child in parent.Children)
{
    Console.WriteLine($"  {child.Caption} ({child.Classname})");
}

Window Manipulation

Show, Hide, and State Changes

using Dapplo.Windows.Desktop;

var window = InteropWindow.FromHandle(handle);

window.Show();
window.Hide();
window.Minimize();
window.Maximize();
window.Restore();

Move and Resize

using Dapplo.Windows.Desktop;
using Dapplo.Windows.Common.Structs;

var window = InteropWindow.FromHandle(handle);

window.MoveTo(new NativePoint(100, 100));
window.Resize(new NativeSize(800, 600));
window.SetPlacement(new NativeRect(100, 100, 900, 700));

Bring to Front

var window = InteropWindow.FromHandle(handle);
window.ToForeground();
window.Flash();    // Flash in the taskbar

Monitoring Window Events

WinEventHook provides a reactive stream of WinEvents. Dispose the subscription when you no longer need it.

Window Creation and Destruction

using Dapplo.Windows.Desktop;

var createSub = WinEventHook.Create(WinEvents.EVENT_OBJECT_CREATE)
    .Subscribe(e =>
    {
        var w = InteropWindow.FromHandle(e.Handle);
        Console.WriteLine($"Created: {w.GetCaption()}");
    });

var destroySub = WinEventHook.Create(WinEvents.EVENT_OBJECT_DESTROY)
    .Subscribe(e => Console.WriteLine($"Destroyed: {e.Handle}"));

// Clean up
createSub.Dispose();
destroySub.Dispose();

Title Changes

WinEventHook.Create(WinEvents.EVENT_OBJECT_NAMECHANGE)
    .Subscribe(e =>
    {
        var w = InteropWindow.FromHandle(e.Handle);
        Console.WriteLine($"Title changed: {w.GetCaption()}");
    });

Foreground Window Changes

WinEventHook.Create(WinEvents.EVENT_SYSTEM_FOREGROUND)
    .Subscribe(e =>
    {
        var w = InteropWindow.FromHandle(e.Handle);
        Console.WriteLine($"Active window: {w.GetCaption()}");
    });

Location / Size Changes

WinEventHook.Create(WinEvents.EVENT_OBJECT_LOCATIONCHANGE)
    .Subscribe(e =>
    {
        var w = InteropWindow.FromHandle(e.Handle);
        w.Fill(InteropWindowRetrieveSettings.Info);
        Console.WriteLine($"Moved/resized: {w.Caption} → {w.Bounds}");
    });

Filtering Events

Use Rx operators to narrow the stream:

using System.Reactive.Linq;

// Only events for a specific window
WinEventHook.Create(WinEvents.EVENT_OBJECT_NAMECHANGE)
    .Where(e => e.Handle == targetHandle)
    .Subscribe(e => Console.WriteLine("Target title changed"));

// Only events for a specific process
WinEventHook.Create(WinEvents.EVENT_OBJECT_CREATE)
    .Where(e => InteropWindow.FromHandle(e.Handle).GetProcessId() == myPid)
    .Subscribe(e => Console.WriteLine("Window created in my process"));

Advanced Scenarios

Find a Window by Title

var window = InteropWindowQuery.GetTopLevelWindows()
    .FirstOrDefault(w => w.GetCaption()?.Contains("Notepad") ?? false);

Z-Order (Stacking Order)

var desktop = InteropWindow.GetDesktopWindow();
desktop.Fill(InteropWindowRetrieveSettings.ZOrderedChildren);

foreach (var w in desktop.ZOrderedChildren.Where(w => w.IsVisible()))
{
    Console.WriteLine(w.Caption);
}

Check Window State

var window = InteropWindow.FromHandle(handle);

Console.WriteLine($"Visible:    {window.IsVisible()}");
Console.WriteLine($"Minimized:  {window.IsMinimized()}");
Console.WriteLine($"Maximized:  {window.IsMaximized()}");
Console.WriteLine($"App window: {window.IsAppWindow()}");

Best Practices

1. Always check validity before using a window handle — windows can be destroyed at any time:

   if (window.Exists())
       Console.WriteLine(window.GetCaption());

2. Dispose subscriptions to avoid memory leaks:

   using var sub = WinEventHook.Create(WinEvents.EVENT_OBJECT_CREATE).Subscribe(...);

3. Cache properties — call Fill() once and use the cached values rather than making repeated API calls.

4. Handle Win32Exception — windows may become invalid between your check and use.

See Also

• Getting-Started
• Common-Scenarios
• GitHub Repository