WinAPI

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Text;

namespace SecureDesktop
{
    public class WinAPI
    {
        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern bool GetExitCodeProcess(IntPtr hProcess, out uint lpExitCode);

        [DllImport("user32.dll")]
        public static extern IntPtr CreateDesktop(string lpszDesktop, IntPtr lpszDevice,
        IntPtr pDevmode, int dwFlags, uint dwDesiredAccess, IntPtr lpsa);

        [DllImport("user32.dll")]
        public static extern bool SwitchDesktop(IntPtr hDesktop);

        [DllImport("user32.dll")]
        public static extern bool CloseDesktop(IntPtr handle);

        [DllImport("user32.dll")]
        public static extern bool SetThreadDesktop(IntPtr hDesktop);

        [DllImport("user32.dll")]
        public static extern IntPtr GetThreadDesktop(int dwThreadId);

        [DllImport("kernel32.dll")]
        public static extern int GetCurrentThreadId();

        [DllImport("kernel32.dll", SetLastError = true)]
        public static extern bool CreateProcess(
            string lpApplicationName, string lpCommandLine, IntPtr lpProcessAttributes, IntPtr lpThreadAttributes, bool bInheritHandles,
            uint dwCreationFlags, IntPtr lpEnvironment, string lpCurrentDirectory, ref STARTUPINFO lpStartupInfo,
            out PROCESS_INFORMATION lpProcessInformation);

        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern bool TerminateProcess(IntPtr hProcess, uint uExitCode);

        public enum DESKTOP_ACCESS : uint
        {
            DESKTOP_NONE = 0,
            DESKTOP_READOBJECTS = 0x0001,
            DESKTOP_CREATEWINDOW = 0x0002,
            DESKTOP_CREATEMENU = 0x0004,
            DESKTOP_HOOKCONTROL = 0x0008,
            DESKTOP_JOURNALRECORD = 0x0010,
            DESKTOP_JOURNALPLAYBACK = 0x0020,
            DESKTOP_ENUMERATE = 0x0040,
            DESKTOP_WRITEOBJECTS = 0x0080,
            DESKTOP_SWITCHDESKTOP = 0x0100,

            GENERIC_ALL = (DESKTOP_READOBJECTS | DESKTOP_CREATEWINDOW | DESKTOP_CREATEMENU |
                            DESKTOP_HOOKCONTROL | DESKTOP_JOURNALRECORD | DESKTOP_JOURNALPLAYBACK |
                            DESKTOP_ENUMERATE | DESKTOP_WRITEOBJECTS | DESKTOP_SWITCHDESKTOP),
#if HOOKS_ENABLED
            CUSTOM_SECURE = (DESKTOP_READOBJECTS | DESKTOP_CREATEWINDOW | DESKTOP_CREATEMENU | DESKTOP_HOOKCONTROL | DESKTOP_WRITEOBJECTS | DESKTOP_SWITCHDESKTOP)
#else
            CUSTOM_SECURE = (DESKTOP_READOBJECTS | DESKTOP_CREATEWINDOW | DESKTOP_CREATEMENU | DESKTOP_WRITEOBJECTS | DESKTOP_SWITCHDESKTOP)
#endif
        }

        public struct PROCESS_INFORMATION
        {
            public IntPtr hProcess;
            public IntPtr hThread;
            public uint dwProcessId;
            public uint dwThreadId;
        }

        public struct STARTUPINFO
        {
            public uint cb;
            public string lpReserved;
            public string lpDesktop;
            public string lpTitle;
            public uint dwX;
            public uint dwY;
            public uint dwXSize;
            public uint dwYSize;
            public uint dwXCountChars;
            public uint dwYCountChars;
            public uint dwFillAttribute;
            public uint dwFlags;
            public short wShowWindow;
            public short cbReserved2;
            public IntPtr lpReserved2;
            public IntPtr hStdInput;
            public IntPtr hStdOutput;
            public IntPtr hStdError;
        }

        public const int
        ULW_ALPHA = 0x00000002,
        WS_EX_LAYERED = 0x00080000,
        WS_EX_TRANSPARENT = 0x00000020,
        WS_EX_TOOLWINDOW = 0x00000080,
        WS_EX_TOPMOST = 0x00000008;

        public const byte AC_SRC_OVER = 0x00;
        public const byte AC_SRC_ALPHA = 0x01;


        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct ARGB
        {
            public byte Blue;
            public byte Green;
            public byte Red;
            public byte Alpha;
        }


        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        public struct BLENDFUNCTION
        {
            public byte BlendOp;
            public byte BlendFlags;
            public byte SourceConstantAlpha;
            public byte AlphaFormat;
        }


        [DllImport("user32.dll", ExactSpelling = true, SetLastError = true)]
        public static extern bool UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst, ref Point pptDst, ref Size psize, IntPtr hdcSrc, ref Point pprSrc, Int32 crKey, ref BLENDFUNCTION pblend, Int32 dwFlags);

        [DllImport("user32.dll", ExactSpelling = true, SetLastError = true)]
        public static extern IntPtr GetDC(IntPtr hWnd);

        [DllImport("user32.dll", ExactSpelling = true)]
        public static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);

        [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
        public static extern IntPtr CreateCompatibleDC(IntPtr hDC);

        [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
        public static extern bool DeleteDC(IntPtr hdc);

        [DllImport("gdi32.dll", ExactSpelling = true)]
        public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);

        [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
        public static extern bool DeleteObject(IntPtr hObject);


        public static IntPtr HWND_TOPMOST = new IntPtr(-1);
        public const int
        SWP_NOSIZE = 0x0001,
        SWP_NOMOVE = 0x0002,
        SWP_SHOWWINDOW = 0x0040;

        [DllImport("user32.dll", SetLastError = true)]
        public static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, int uFlags);

        public enum ShowCommands : int
        {
            SW_HIDE = 0,
            SW_SHOWNORMAL = 1,
            SW_NORMAL = 1,
            SW_SHOWMINIMIZED = 2,
            SW_SHOWMAXIMIZED = 3,
            SW_MAXIMIZE = 3,
            SW_SHOWNOACTIVATE = 4,
            SW_SHOW = 5,
            SW_MINIMIZE = 6,
            SW_SHOWMINNOACTIVE = 7,
            SW_SHOWNA = 8,
            SW_RESTORE = 9,
            SW_SHOWDEFAULT = 10,
            SW_FORCEMINIMIZE = 11,
            SW_MAX = 11
        }

        [DllImport("shell32.dll")]
        public static extern IntPtr ShellExecute(
            IntPtr hwnd,
            string lpOperation,
            string lpFile,
            string lpParameters,
            string lpDirectory,
            ShowCommands nShowCmd);

        [DllImport("Shlwapi.dll", SetLastError = true, CharSet = CharSet.Auto)]
        public static extern uint AssocQueryString(AssocF flags, AssocStr str, string pszAssoc, string pszExtra, [Out] StringBuilder pszOut, ref uint pcchOut);

        [Flags]
        public enum AssocF : uint
        {
            None = 0,
            Init_NoRemapCLSID = 0x1,
            Init_ByExeName = 0x2,
            Open_ByExeName = 0x2,
            Init_DefaultToStar = 0x4,
            Init_DefaultToFolder = 0x8,
            NoUserSettings = 0x10,
            NoTruncate = 0x20,
            Verify = 0x40,
            RemapRunDll = 0x80,
            NoFixUps = 0x100,
            IgnoreBaseClass = 0x200,
            Init_IgnoreUnknown = 0x400,
            Init_FixedProgId = 0x800,
            IsProtocol = 0x1000,
            InitForFile = 0x2000,
        }

        public enum AssocStr
        {
            Command = 1,
            Executable,
            FriendlyDocName,
            FriendlyAppName,
            NoOpen,
            ShellNewValue,
            DDECommand,
            DDEIfExec,
            DDEApplication,
            DDETopic,
            InfoTip,
            QuickTip,
            TileInfo,
            ContentType,
            DefaultIcon,
            ShellExtension,
            DropTarget,
            DelegateExecute,
            SupportedUriProtocols,
            Max,
        }

        public const int S_OK = 0, S_FALSE = 1;

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
        public class MEMORYSTATUSEX
        {
            public uint dwLength;
            public uint dwMemoryLoad;
            public ulong ullTotalPhys;
            public ulong ullAvailPhys;
            public ulong ullTotalPageFile;
            public ulong ullAvailPageFile;
            public ulong ullTotalVirtual;
            public ulong ullAvailVirtual;
            public ulong ullAvailExtendedVirtual;
            public MEMORYSTATUSEX()
            {
                this.dwLength = (uint)Marshal.SizeOf(typeof(MEMORYSTATUSEX));
            }
        }

        [return: MarshalAs(UnmanagedType.Bool)]
        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern bool GlobalMemoryStatusEx([In, Out] MEMORYSTATUSEX lpBuffer);

        [StructLayout(LayoutKind.Sequential)]
        public struct POINT
        {
            public int X;
            public int Y;
        }

        [DllImport("user32.dll")]
        public static extern bool GetCursorPos(out POINT lpPoint);

        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        public static extern bool GetDiskFreeSpace(string lpRootPathName,
           out uint lpSectorsPerCluster,
           out uint lpBytesPerSector,
           out uint lpNumberOfFreeClusters,
           out uint lpTotalNumberOfClusters);
    }
}