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How to get focused window handler

I have a WPF custom virtual keyboard application. I need to host this WPF application as standalone and user should be able to use this to enter values for any window application.
How to get the current focused application window? ex: notepad, notepad++ or any other window applications which takes in input.
I have tried below code to get the current active window, but it returns the WPF virtual keyboard application itself since it is also in active state
var window = System.Windows.Application.Current.Windows.OfType<Window>().SingleOrDefault(w => w.IsActive);
The below code works fine however, this requires windowname as param to set the foregroundwindow
public partial class MainWindow : Window{
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool SetForegroundWindow(IntPtr hWnd);
[DllImport("user32.dll", EntryPoint = "FindWindow", SetLastError = true)]
static extern IntPtr FindWindowByCaption(IntPtr ZeroOnly, string lpWindowName);
private void button1_Click(object sender, RoutedEventArgs e){
SetForegroundWindow(FindWindowByCaption(IntPtr.Zero, "Untitled - Notepad"));
}
}

To get the current active window handle, you could use GetForegroundWindow from the user32.dll.
In C# it should look something like
[DllImport("user32.dll")]
static extern IntPtr GetForegroundWindow();
Or in case your application window will be the active window, you could use GetWindow
[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr GetWindow(IntPtr hWnd, GetWindow_Cmd uCmd);
enum GetWindow_Cmd : uint {
GW_HWNDFIRST = 0,
GW_HWNDLAST = 1,
GW_HWNDNEXT = 2,
GW_HWNDPREV = 3,
GW_OWNER = 4,
GW_CHILD = 5,
GW_ENABLEDPOPUP = 6
}
So you could pass your own window handle as first argument and GW_HWNDNEXT as second. As a result you get the handle for the window that is below your current window.
EDIT
As IInspectable mentioned, the above won't work within an WPF application.
But you could try using the following using EnumWindows:
// Get own hWnd
WindowInteropHelper windowHwnd = new(this);
IntPtr ownHwnd = windowHwnd.Handle;
// Find target hWnd
IntPtr targetHWnd = IntPtr.Zero;
NativeMethods.EnumWindows((hWnd, lParam) =>
{
if (hWnd == ownHwnd) { return true; } // Ignore own window
if (!NativeMethods.IsWindowVisible(hWnd)) { return true; } // Ignore hidden windows
if (GetClassName(hWnd).Equals("Shell_TrayWnd", StringComparison.OrdinalIgnoreCase)) { return true; } // Ignore taskbar window
if (string.IsNullOrEmpty(GetWindowTitle(hWnd))) { return true; } // Ignore windows without a title
targetHWnd = hWnd; // Found target hWnd
return false; // Stop iterating
}, IntPtr.Zero);
// Used functions
private string GetWindowTitle(IntPtr hWnd)
{
int textLength = NativeMethods.GetWindowTextLength(hWnd);
StringBuilder sb = new(textLength + 1);
NativeMethods.GetWindowText(hWnd, sb, sb.Capacity);
return sb.ToString();
}
private string GetClassName(IntPtr hWnd)
{
StringBuilder sb = new(256);
NativeMethods.GetClassName(hWnd, sb, sb.Capacity);
return sb.ToString().Trim();
}
internal static class NativeMethods
{
[DllImport("user32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
internal static extern bool IsWindowVisible(IntPtr hWnd);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
internal static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);
[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
internal static extern int GetWindowTextLength(IntPtr hWnd);
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
internal static extern bool EnumWindows(EnumWindowsProc lpEnumFunc, IntPtr lParam);
internal delegate bool EnumWindowsProc(IntPtr hWnd, IntPtr lParam);
[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
internal static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);
}
Edit 2
To ensure the WPF hWnd is created, you could use WindowInteropHelper.EnsureHandle() method instead of the Handle property. This is important if the WPF window has not been displayed yet.

Sending keys to background window (not notepad)

So I've been stuck for about 10 hours now. This code works perfectly for notepad. It sends the keystrokes to notepad in the background without having to click on it or anything. Problem is, no other window or process works and I've no idea why. I tried changing the names and using the window name instead of the process name stuff like that and nothing works. Only Notepad.
No, I can't use SendKeys because I need this to be in the background.
[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);
[DllImport("user32.dll")]
private static extern bool PostMessage(
IntPtr hWnd, // handle to destination window
UInt32 Msg, // message
Int32 wParam, // first message parameter
Int32 lParam // second message parameter
);
public void Start()
{
const int WM_KEYDOWN = 0x100;
// IntPtr Notepad = FindWindow(null, "");
//Console.WriteLine(Notepad);
Process notepadProccess = Process.GetProcessesByName("notepad")[0];
Console.WriteLine(notepadProccess.MainWindowHandle);
Console.WriteLine(notepadProccess.MainWindowTitle);
IntPtr editx = FindWindowEx(notepadProccess.MainWindowHandle, IntPtr.Zero, "Edit", null);
PostMessage(editx, WM_KEYDOWN, (int)Keys.X, 0);
}

Can't toggle 'Align icons to grid' on the desktop

Here's the code I'm using:
private void Button_Click(object sender, RoutedEventArgs e) {
SendMessage(GetDesktopWindow(), LVM_ARRANGE, LVA_SNAPTOGRID, 0);
}
public const uint LVM_ARRANGE = 0x1000 + 22;
public const int LVA_SNAPTOGRID = 0x0005;
[DllImport("User32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr GetDesktopWindow();
[DllImport("user32.dll")]
public static extern int SendMessage(IntPtr hWnd, uint msg, int wParam, int lParam);
Nothing happens when I run it. Code is borrowed from https://www.codeproject.com/Messages/1168961/Re-Auto-Arrange-desktop-icons.aspx
Tried different Windows versions too.

This code worked for me. Note that it doesn't appear to change the options, so although it arranges to the grid for me the View->Align Icons To Grid is still unchecked. The issue is outlined here: How do I get the window handle of the desktop?
Your problem results from a fairly widespread confusion over what the
desktop window actually is. The GetDesktopWindow function does
precisely what it's documented to do: it returns a handle to the
desktop window. This, however, is not the same window that contains
the desktop icons.
So I used the answer here: Get handle to desktop / shell window but with replacing or adding methods and p/invoke calls until I had everything necessary because that link only gives method calls and not the dll imports (I may have left some superfluous stuff in here).
static void Main()
{
SendMessage(GetDesktopWindow(DesktopWindow.SysListView32), LVM_ARRANGE, LVA_SNAPTOGRID, 0);
Console.ReadLine();
}
public const int LVM_ARRANGE = 4118;
public const int LVA_SNAPTOGRID = 5;
[DllImport("user32.dll")]
static extern IntPtr GetShellWindow();
[DllImport("user32.dll", CharSet = CharSet.Unicode)]
static extern IntPtr FindWindowEx(IntPtr parentHandle, IntPtr childAfter, string lclassName, string windowTitle);
[DllImport("User32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr GetDesktopWindow();
[DllImport("user32.dll")]
public static extern int SendMessage(IntPtr hWnd, uint msg, int wParam, int lParam);
[DllImport("user32.dll")]
private static extern bool EnumWindows(EnumWindowsProc enumProc, IntPtr lParam);
public delegate bool EnumWindowsProc(IntPtr hWnd, IntPtr lParam);
[DllImport("user32.dll", CharSet = CharSet.Unicode)]
private static extern int GetWindowText(IntPtr hWnd, StringBuilder strText, int maxCount);
[DllImport("user32.dll", CharSet = CharSet.Unicode)]
private static extern int GetWindowTextLength(IntPtr hWnd);
public enum DesktopWindow
{
ProgMan,
SHELLDLL_DefViewParent,
SHELLDLL_DefView,
SysListView32
}
public static IntPtr GetDesktopWindow(DesktopWindow desktopWindow)
{
IntPtr _ProgMan = GetShellWindow();
IntPtr _SHELLDLL_DefViewParent = _ProgMan;
IntPtr _SHELLDLL_DefView = FindWindowEx(_ProgMan, IntPtr.Zero, "SHELLDLL_DefView", null);
IntPtr _SysListView32 = FindWindowEx(_SHELLDLL_DefView, IntPtr.Zero, "SysListView32", "FolderView");
if (_SHELLDLL_DefView == IntPtr.Zero)
{
EnumWindows((hwnd, lParam) =>
{
if (GetWindowText(hwnd) == "WorkerW")
{
IntPtr child = FindWindowEx(hwnd, IntPtr.Zero, "SHELLDLL_DefView", null);
if (child != IntPtr.Zero)
{
_SHELLDLL_DefViewParent = hwnd;
_SHELLDLL_DefView = child;
_SysListView32 = FindWindowEx(child, IntPtr.Zero, "SysListView32", "FolderView"); ;
return false;
}
}
return true;
}, IntPtr.Zero);
}
switch (desktopWindow)
{
case DesktopWindow.ProgMan:
return _ProgMan;
case DesktopWindow.SHELLDLL_DefViewParent:
return _SHELLDLL_DefViewParent;
case DesktopWindow.SHELLDLL_DefView:
return _SHELLDLL_DefView;
case DesktopWindow.SysListView32:
return _SysListView32;
default:
return IntPtr.Zero;
}
}
public static string GetWindowText(IntPtr hWnd)
{
int size = GetWindowTextLength(hWnd);
if (size > 0)
{
var builder = new StringBuilder(size + 1);
GetWindowText(hWnd, builder, builder.Capacity);
return builder.ToString();
}
return String.Empty;
}

How to change the button text of another programs window

I have been tasked with changing the text of a button in a window. I don't have and cannot access the source code as it's owned by a company we have a paid subscription with.
How can I change the button text with no source code? I'm trying with pInvoke and having problems. The window title changes depending on who you are working with:
"Order Entry Sheet - LASTNAME, FIRSTNAME"
So the window title may not be useable for me inside of the win32 call
FindWindow(string lpClassName, string lpWindowName);
I know both params are optional. I'm using Spy++ and I'm not sure what to use for lpClassName. The class name I see listed is #32770 (Dialog). I tried it and got a return of 0.
IntPtr windowHandle = FindWindow("#32770 (Dialog)", null);
How can I change the button text from another process?
UPDATE
According to MSDN I should be able to achieve this via SetWindowText.
Changes the text of the specified window's title bar (if it has one).
If the specified window is a control, the text of the control is
changed. However, SetWindowText cannot change the text of a control in
another application.
I can't use SetWindowText to do what I want. Is it possible to use something else?

[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);
[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
static extern int GetWindowTextLength(IntPtr hWnd);
[DllImport("user32", SetLastError = true)]
public static extern int EnumWindows(CallBack x, int y);
[DllImport("user32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool EnumChildWindows(IntPtr hwndParent, CallBack lpEnumFunc, IntPtr lParam);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern IntPtr SendMessage(HandleRef hWnd, uint Msg, IntPtr wParam, string lParam);
public const uint WM_SETTEXT = 0x000C;
public delegate bool CallBack(int hwnd, int lParam);
public static void Main()
{
CallBack windowsCallback = new CallBack(IterateWindows);
EnumWindows(windowsCallback, 0);
}
public static bool IterateChildren(int hwnd, int lParam)
{
string newButtonText = "Some text";
bool continueIteratingChildren = true;
//Console.WriteLine("Child handle: " + hwnd);
int length = GetWindowTextLength((IntPtr)hwnd);
StringBuilder sb = new StringBuilder(length + 1);
GetWindowText((IntPtr)hwnd, sb, sb.Capacity);
//Console.WriteLine(sb);
if (sb.ToString().StartsWith("My Button Text "))
{
HandleRef hrefHWndTarget = new HandleRef(null, (IntPtr)hwnd);
SendMessage(hrefHWndTarget, WM_SETTEXT, IntPtr.Zero, newButtonText);
continueIteratingChildren = false;
}
return continueIteratingChildren;
}
public static bool IterateWindows(int hwnd, int lParam)
{
bool continueIteratingWindows = true;
int windowTextLength = GetWindowTextLength((IntPtr)hwnd);
StringBuilder sb = new StringBuilder(windowTextLength + 1);
GetWindowText((IntPtr)hwnd, sb, sb.Capacity);
if (sb.ToString().StartsWith("My Window Caption"))
{
//Console.Write("Window handle is ");
//Console.WriteLine(hwnd);
//Console.WriteLine(sb);
//Console.WriteLine(Marshal.GetLastWin32Error());
var childrenCallback = new CallBack(IterateChildren);
EnumChildWindows((IntPtr)hwnd, childrenCallback, IntPtr.Zero);
continueIteratingWindows = false;
}
return continueIteratingWindows;
}

Windows 7 left click on clock popup

When left single click on the clock in the taskbar on Windows 7 (maybe Vista too) a popup opens showing calender and clock(s) (thus not the date and time adjust window). How do I open this window myself (preferred in C#)?
I was hoping timedate.cpl would call this, but this opens the date and time adjust window.

To show the clock you need to send the appropriate window message to the tray window. This can be done using the Windows API function SendMessage:
using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Text;
class ShowCalendar
{
private delegate bool EnumChildCallback(IntPtr hwnd,
ref IntPtr lParam);
[DllImport("User32.dll")]
private static extern bool EnumChildWindows(IntPtr hWndParent,
EnumChildCallback lpEnumFunc,
ref IntPtr lParam);
[DllImport("User32.dll")]
private static extern int GetClassName(IntPtr hWnd,
StringBuilder lpClassName,
int nMaxCount);
[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern IntPtr SendMessage(IntPtr hWnd,
UInt32 Msg,
IntPtr wParam,
IntPtr lParam);
[DllImport("user32.dll", SetLastError = true)]
private static extern IntPtr FindWindow(string lpClassName,
string lpWindowName);
[DllImport("user32.dll", SetLastError = true)]
private static extern IntPtr FindWindowEx(IntPtr hwndParent,
IntPtr hwndChildAfter,
string lpszClass,
string lpszWindow);
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool GetWindowRect(IntPtr hWnd,
out RECT lpRect);
[StructLayout(LayoutKind.Sequential)]
private struct RECT
{
public int Left;
public int Top;
public int Right;
public int Bottom;
}
private static readonly string TrayWndClassName = "Shell_TrayWnd";
private static readonly string TrayNotifyWndClassName = "TrayNotifyWnd";
private static readonly string ClockWndClassName = "TrayClockWClass";
private static readonly uint WM_NCLBUTTONDOWN = 0x00A1;
private static readonly uint HTCAPTION = 2;
private static bool EnumChildProc(IntPtr hwndChild, ref IntPtr lParam)
{
StringBuilder className = new StringBuilder(128);
GetClassName(hwndChild, className, 128);
if (className.ToString() == ClockWndClassName)
{
lParam = hwndChild;
return false;
}
return true;
}
static void Main(string[] args)
{
IntPtr hWndTray = FindWindow(TrayWndClassName, string.Empty);
if (hWndTray == IntPtr.Zero)
{
throw new Win32Exception();
}
IntPtr hWndTrayNotify = FindWindowEx(hWndTray,
IntPtr.Zero,
TrayNotifyWndClassName,
string.Empty);
if (hWndTrayNotify == IntPtr.Zero)
{
throw new Win32Exception();
}
// search clock window
EnumChildCallback cb = new EnumChildCallback(EnumChildProc);
IntPtr hWndClock = IntPtr.Zero;
EnumChildWindows(hWndTray, cb, ref hWndClock);
if (hWndClock == IntPtr.Zero)
{
throw new Win32Exception();
}
// get clock window position
RECT rect;
if (!GetWindowRect(hWndClock, out rect))
{
throw new Win32Exception();
}
// send click, lParam contains window position
IntPtr wParam = new IntPtr(HTCAPTION);
IntPtr lParam = new IntPtr(rect.Top << 16 | rect.Left);
SendMessage(hWndTray, WM_NCLBUTTONDOWN, wParam, lParam);
}
}