DevDrive/DriveHider.cs

using System.Runtime.Versioning;
using Microsoft.Win32;

namespace DevDrive;

/// <summary>
/// Handles hiding and showing drives from Windows Explorer using registry.
/// </summary>
[SupportedOSPlatform("windows")]
public static class DriveHider
{
    private const string LogPrefix = "[DriveHider]";
    private const string ExplorerPoliciesKey = @"Software\Microsoft\Windows\CurrentVersion\Policies\Explorer";
    private const string NoDrivesValue = "NoDrives";

    private static int _hiddenDriveMask;
    private static string? _hiddenDriveLetter;
    private static int _originalNoDrives;

    public static bool HideDrive(string driveLetter)
    {
        if (_hiddenDriveLetter != null)
        {
            Console.WriteLine($"{LogPrefix} Drive already hidden");
            return true;
        }

        try
        {
            var letter = driveLetter.TrimEnd('\\', ':').ToUpperInvariant();
            if (letter.Length != 1 || letter[0] < 'A' || letter[0] > 'Z')
            {
                Console.WriteLine($"{LogPrefix} Invalid drive letter: {driveLetter}");
                return false;
            }

            var driveIndex = letter[0] - 'A';
            _hiddenDriveMask = 1 << driveIndex;
            _hiddenDriveLetter = letter + ":\\";

            using var key = Registry.CurrentUser.CreateSubKey(ExplorerPoliciesKey);
            if (key == null)
            {
                Console.WriteLine($"{LogPrefix} Failed to open registry key");
                return false;
            }

            _originalNoDrives = GetNoDrivesValue(key);
            var newValue = _originalNoDrives | _hiddenDriveMask;

            key.SetValue(NoDrivesValue, newValue, RegistryValueKind.DWord);

            RefreshExplorer();

            Console.WriteLine($"{LogPrefix} Hidden drive {letter}: from Explorer");
            return true;
        }
        catch (Exception ex)
        {
            Console.WriteLine($"{LogPrefix} Error hiding drive: {ex.Message}");
            _hiddenDriveMask = 0;
            _hiddenDriveLetter = null;
            return false;
        }
    }

    public static bool ShowDrive()
    {
        if (_hiddenDriveLetter == null)
        {
            return true;
        }

        try
        {
            using var key = Registry.CurrentUser.OpenSubKey(ExplorerPoliciesKey, writable: true);
            if (key == null)
            {
                Console.WriteLine($"{LogPrefix} Failed to open registry key for restore");
                return false;
            }

            var currentValue = GetNoDrivesValue(key);
            var newValue = currentValue & ~_hiddenDriveMask;

            if (newValue == 0)
            {
                key.DeleteValue(NoDrivesValue, throwOnMissingValue: false);
            }
            else
            {
                key.SetValue(NoDrivesValue, newValue, RegistryValueKind.DWord);
            }

            RefreshExplorer();

            Console.WriteLine($"{LogPrefix} Restored drive {_hiddenDriveLetter.TrimEnd('\\')} in Explorer");
            _hiddenDriveMask = 0;
            _hiddenDriveLetter = null;
            return true;
        }
        catch (Exception ex)
        {
            Console.WriteLine($"{LogPrefix} Error restoring drive: {ex.Message}");
            return false;
        }
    }

    public static bool IsHidden => _hiddenDriveLetter != null;
    public static string? HiddenDriveLetter => _hiddenDriveLetter;

    private static int GetNoDrivesValue(RegistryKey key)
    {
        var value = key.GetValue(NoDrivesValue);
        
        return value switch
        {
            null => 0,
            int intValue => intValue,
            uint uintValue => (int)uintValue,
            byte[] bytes when bytes.Length >= 4 => BitConverter.ToInt32(bytes, 0),
            byte[] bytes when bytes.Length > 0 => bytes[0],
            _ => 0
        };
    }

    private static void RefreshExplorer()
    {
        try
        {
            NativeMethods.SendMessageTimeout(
                NativeMethods.HWND_BROADCAST,
                NativeMethods.WM_SETTINGCHANGE,
                IntPtr.Zero,
                "Policy",
                NativeMethods.SMTO_ABORTIFHUNG,
                1000,
                out _);

            NativeMethods.SHChangeNotify(
                NativeMethods.SHCNE_DRIVEADD | NativeMethods.SHCNE_DRIVEREMOVED,
                NativeMethods.SHCNF_FLUSHNOWAIT,
                IntPtr.Zero,
                IntPtr.Zero);
        }
        catch
        {
        }
    }

    private static class NativeMethods
    {
        public const int SHCNE_DRIVEADD = 0x00000100;
        public const int SHCNE_DRIVEREMOVED = 0x00000080;
        public const int SHCNF_FLUSHNOWAIT = 0x3000;
        
        public static readonly IntPtr HWND_BROADCAST = new(0xFFFF);
        public const int WM_SETTINGCHANGE = 0x001A;
        public const int SMTO_ABORTIFHUNG = 0x0002;

        [System.Runtime.InteropServices.DllImport("shell32.dll")]
        public static extern void SHChangeNotify(int wEventId, int uFlags, IntPtr dwItem1, IntPtr dwItem2);

        [System.Runtime.InteropServices.DllImport("user32.dll", SetLastError = true, CharSet = System.Runtime.InteropServices.CharSet.Auto)]
        public static extern IntPtr SendMessageTimeout(
            IntPtr hWnd,
            int Msg,
            IntPtr wParam,
            string lParam,
            int fuFlags,
            int uTimeout,
            out IntPtr lpdwResult);
    }
}