A failing example of hooking `Win` + `Tab`: Behaves as if the `Win` key was still down

WinTabHookExample.cs

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

namespace WinTabHookExample
{
	public static class Program
	{
		[StructLayout(LayoutKind.Sequential)]
		public struct Kbdllhookstruct
		{
			public int VkCode;
			public int ScanCode;
			public int Flags;
			public int Time;
			public IntPtr Extra;
		}

		[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
		private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

		[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
		[return: MarshalAs(UnmanagedType.Bool)]
		private static extern bool UnhookWindowsHookEx(IntPtr hhk);

		[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
		private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);

		[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
		private static extern IntPtr GetModuleHandle(string lpModuleName);

		private const int HC_ACTION = 0;
		private const int WH_KEYBOARD_LL = 13;
		private const int WM_KEYDOWN = 0x0100;
		private const int WM_KEYUP = 0x0101;
		private const int VK_LWIN = 0x5B;
		private const int VK_TAB = 0x09;

		private static IntPtr _hookID = IntPtr.Zero;
		private static bool _isWinDown;
		private static bool _isWinTabDetected;
		
		private static int _winTabPressCounter;
		private static Form1 _mainForm;

		private delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);

		[STAThread]
		static void Main()
		{
			try
			{
				var proc = new LowLevelKeyboardProc(HookCallback);

				using (var curProcess = Process.GetCurrentProcess())
				{
					using (var curModule = curProcess.MainModule)
					{
						_hookID = SetWindowsHookEx(WH_KEYBOARD_LL, proc, GetModuleHandle(curModule.ModuleName), 0);
					}
				}

				Application.EnableVisualStyles();
				Application.SetCompatibleTextRenderingDefault(false);
				_mainForm = new Form1 {Width = 640};
				Application.Run(_mainForm);
			}
			finally
			{
				UnhookWindowsHookEx(_hookID);
			}
		}

		private static IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
		{
			if (nCode != HC_ACTION)
				return CallNextHookEx(_hookID, nCode, wParam, lParam);

			var keyInfo = (Kbdllhookstruct)Marshal.PtrToStructure(lParam, typeof(Kbdllhookstruct));

			if (keyInfo.VkCode == VK_LWIN)
			{
				if (wParam == (IntPtr)WM_KEYDOWN)
				{
					_isWinDown = true;
				}
				else
				{
					_isWinDown = false;

					if (_isWinTabDetected)
					{
						_isWinTabDetected = false;
						return (IntPtr)1;
					}
				}
			}
			else if (keyInfo.VkCode == VK_TAB && _isWinDown)
			{
				_isWinTabDetected = true;

				if (wParam == (IntPtr)WM_KEYDOWN)
				{
					return (IntPtr)1;
				}
				else
				{
					_isWinTabDetected = true;
					_mainForm.Text = "Win + Tab was pressed " + (++_winTabPressCounter) + " times";
					return (IntPtr)1;
				}
			}

			return CallNextHookEx(_hookID, nCode, wParam, lParam);
		}
	}
}