wpf c# check Enter key and PrtSc pressed

Question

wpf c# check Enter key and PrtSc pressed

hossein tavakoli 471

Hi dears,

I'm using WPF/C# to create a application for checking keyboard's key work correctly.

I have problems with 3 key:

1- Enter Key (placed inside numeric key) : Enter key I can see IsExtended property in debugging mode but I don't have access it in code.

2- PrtSc key : when I press it windows screenshot app will open and I can't check it pressed.

3- Win key : I can check it but after key press start menu will open, I want to check win key pressed without opening start menu.

my code is here :

private void tabItemKeyboard_PreviewKeyDown(object sender, System.Windows.Input.KeyEventArgs e)
{
	string key = (e.Key == Key.System) ? e.SystemKey.ToString() : e.Key.ToString();
	txtKeyPress.Content = key;
	FindLabelKeyPressed(key);
	if (LabelSelected != null)
	{
		LabelSelected.Background = System.Windows.Media.Brushes.Yellow;
	}
	if (key == "F10" || key.ToLower().Contains("alt") || key.ToLower()=="left" || key.ToLower()== "right" || key.ToLower().Contains("home") || key.ToLower().Contains("win"))
		e.Handled = true;
}

please give me a code.

1 answer

Your answer

Answer 1

KOZ6.0 6,735

The PrintScreen key can be detected with keyboard hooks. Call the SetWindowsHookEx API to install the ~~WH_MOUSE_LL~~ WH_KEYBOARD_LL hook.

SetWindowsHookExW

You can also check whether a key is pressed using the GetKeyState API.

GetKeyState function (winuser.h)

KOZ6.0 6,735 Reputation points

2023-10-25T14:29:38.49+00:00

Sorry, I have a sample, but it's in VB and for Windows Forms. I don't have time to rewrite it.

https://gist.github.com/KOZ60/f3d4706c830ef31d333b41132baa63a8
hossein tavakoli 471 Reputation points

2023-10-25T17:27:40.8333333+00:00

could you give me a c# sample please

KOZ6.0 6,735

This is for Windows Forms. Please do the rewriting to WPF yourself.

using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Windows.Forms;

[DesignerCategory("code")]
[DefaultEvent("KeyDown")]
public class LowLevelKeyboardHook : Component
{

	private IntPtr HookHandle = IntPtr.Zero;

	private LowLevelKeyboardProcDelegate HookProcHandle;
	public event KeyEventHandler KeyDown;
	public event KeyEventHandler KeyUp;

	public LowLevelKeyboardHook()
	{
	}

	public LowLevelKeyboardHook(IContainer container) : this()
	{
		if (container == null) {
			throw new ArgumentNullException("container");
		}
		container.Add(this);
	}

	public void Start()
	{
		if (HookHandle == IntPtr.Zero) {
			HookProcHandle = LowLevelKeyboardProc;
			HookHandle = SetWindowsHookEx(WH_KEYBOARD_LL, HookProcHandle, GetModuleHandle(null), 0);
		}
	}

	public void Stop()
	{
		if (HookHandle != IntPtr.Zero) {
			UnhookWindowsHookEx(HookHandle);
			HookProcHandle = null;
			HookHandle = IntPtr.Zero;
		}
	}

	protected override void Dispose(bool disposing)
	{
		base.Dispose(disposing);
		this.Stop();
	}


	private IntPtr LowLevelKeyboardProc(int code, IntPtr wParam, IntPtr lparam)
	{
		try {
			if (code == HC_ACTION) {
				KBDLLHOOKSTRUCT st = Marshal.PtrToStructure<KBDLLHOOKSTRUCT>(lparam);
				Keys vkCode = st.vkCode | Control.ModifierKeys;
				KeyEventArgs ke = new KeyEventArgs(vkCode);
				switch (wParam.ToInt64()) {
					case WM_KEYDOWN:
						OnKeyDown(ke);
						break;
					case WM_KEYUP:
						OnKeyUp(ke);
						break;
				}
			}
		} finally {
		}
		return CallNextHookEx(HookHandle, code, wParam, lparam);
	}

	protected virtual void OnKeyDown(KeyEventArgs ke)
	{
		if (KeyDown != null) {
			KeyDown(this, ke);
		}
	}

	protected virtual void OnKeyUp(KeyEventArgs ke)
	{
		if (KeyUp != null) {
			KeyUp(this, ke);
		}
	}

	private const string User32 = "user32.dll";
	private const string Kernel32 = "kernel32.dll";

	private const int WH_KEYBOARD_LL = 13;
	private const int HC_ACTION = 0;
	private const int WM_KEYDOWN = 0x100;

	private const int WM_KEYUP = 0x101;
	private delegate IntPtr LowLevelKeyboardProcDelegate(int code, IntPtr wParam, IntPtr lparam);

	[StructLayout(LayoutKind.Sequential)]
	private struct KBDLLHOOKSTRUCT
	{
		public Keys vkCode;
		public Keys scanCode;
		public int flags;
		public int time;
		public IntPtr dwExtraInfo;
	}

	[DllImport(User32, CharSet = CharSet.Auto)]
	private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProcDelegate lpfn, IntPtr hInstance, int threadId);

	[DllImport(User32, CharSet = CharSet.Auto)]
	[return: MarshalAs(UnmanagedType.Bool)]
	private static extern bool UnhookWindowsHookEx(IntPtr hhk);

	[DllImport(User32, CharSet = CharSet.Auto)]
	private static extern IntPtr CallNextHookEx(IntPtr idHook, int code, IntPtr wParam, IntPtr lparam);

	[DllImport(Kernel32, CharSet = CharSet.Auto)]
	private static extern IntPtr GetModuleHandle(string lpModuleName);

}

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wpf c# check Enter key and PrtSc pressed

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