Create a system tray icon and a dialog for a Windows Service

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

namespace SystemTrayIconInSvc
{
    /// <summary>
    /// The wrapper class for User32.dll
    /// </summary>
    public static class User32DLL
    {
        /// <summary>
        /// The GetDesktopWindow function returns a handle to the desktop window. The desktop window covers the entire screen. The desktop window is the area on top of which other windows are painted. 
        /// </summary>
        /// <returns>The return value is a handle to the desktop window. </returns>
        [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern IntPtr GetDesktopWindow();


        /// <summary>
        /// Retrieves a handle to the current window station for the calling process.
        /// </summary>
        /// <returns>If the function succeeds, the return value is a handle to the window station.
        /// If the function fails, the return value is NULL.</returns>
        [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern IntPtr GetProcessWindowStation();


        /// <summary>
        /// Retrieves a handle to the desktop assigned to the specified thread.
        /// </summary>
        /// <param name="dwThread">[in] Handle to the thread for which to return the desktop handle.</param>
        /// <returns>If the function succeeds, the return value is a handle to the desktop associated with the specified thread. You do not need to call the CloseDesktop function to close the returned handle.
        /// If the function fails, the return value is NULL.</returns>
        [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern IntPtr GetThreadDesktop(uint dwThread);


        /// <summary>
        /// Opens the specified window station.
        /// </summary>
        /// <param name="lpszWinSta">Pointer to a null-terminated string specifying the name of the window station to be opened. Window station names are case-insensitive.
        /// This window station must belong to the current session.
        /// </param>
        /// <param name="fInherit">[in] If this value is TRUE, processes created by this process will inherit the handle. Otherwise, the processes do not inherit this handle. 
        /// </param>
        /// <param name="dwDesiredAccess">[in] Access to the window station</param>
        /// <returns>If the function succeeds, the return value is the handle to the specified window station.
        /// If the function fails, the return value is NULL.</returns>
        [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern IntPtr OpenWindowStation(string lpszWinSta
            , bool fInherit
            , WindowStationAccessRight dwDesiredAccess
            );


        /// <summary>
        /// Assigns the specified window station to the calling process. This enables the process to access objects in the window station such as desktops, the clipboard, and global atoms. All subsequent operations on the window station use the access rights granted to hWinSta.
        /// </summary>
        /// <param name="hWinSta">[in] Handle to the window station to be assigned to the calling process</param>
        /// <returns>If the function succeeds, the return value is nonzero.
        /// If the function fails, the return value is zero. </returns>
        [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern IntPtr SetProcessWindowStation(IntPtr hWinSta);


        /// <summary>
        /// Closes an open window station handle.
        /// </summary>
        /// <param name="hWinSta">[in] Handle to the window station to be closed.</param>
        /// <returns>If the function succeeds, the return value is nonzero.
        /// If the function fails, the return value is zero. </returns>
        [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern IntPtr CloseWindowStation(IntPtr hWinSta);


        /// <summary>
        /// Opens the specified desktop object.
        /// </summary>
        /// <param name="lpszDesktop">[in] Pointer to null-terminated string specifying the name of the desktop to be opened. Desktop names are case-insensitive.
        /// This desktop must belong to the current window station.</param>
        /// <param name="dwFlags">[in] This parameter can be zero or DF_ALLOWOTHERACCOUNTHOOK=0x0001</param>
        /// <param name="fInherit">[in] If this value is TRUE, processes created by this process will inherit the handle. Otherwise, the processes do not inherit this handle. </param>
        /// <param name="dwDesiredAccess">[in] Access to the desktop. For a list of access rights</param>
        /// <returns>If the function succeeds, the return value is a handle to the opened desktop. When you are finished using the handle, call the CloseDesktop function to close it.
        /// If the function fails, the return value is NULL.
        /// </returns>
        [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern IntPtr OpenDesktop(string lpszDesktop
            , OpenDesktopFlag dwFlags
            , bool fInherit
            , DesktopAccessRight dwDesiredAccess
            );


        /// <summary>
        /// Closes an open handle to a desktop object.
        /// </summary>
        /// <param name="hDesktop">[in] Handle to the desktop to be closed.</param>
        /// <returns>If the function succeeds, the return value is nonzero.
        /// If the function fails, the return value is zero. </returns>
        [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern IntPtr CloseDesktop(IntPtr hDesktop);

        /// <summary>
        /// Assigns the specified desktop to the calling thread. All subsequent operations on the desktop use the access rights granted to the desktop.
        /// </summary>
        /// <param name="hDesktop">[in] Handle to the desktop to be assigned to the calling thread.</param>
        /// <returns>If the function succeeds, the return value is nonzero.
        /// If the function fails, the return value is zero. </returns>
        [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern bool SetThreadDesktop(IntPtr hDesktop);
    }


    /// <summary>
    /// REF MSDN:Window Station Security and Access Rights
    /// ms-help://MS.MSDN.vAug06.en/dllproc/base/window_station_security_and_access_rights.htm
    /// </summary>
    [FlagsAttribute]
    public enum WindowStationAccessRight : uint
    {
        /// <summary>All possible access rights for the window station.</summary>
        WINSTA_ALL_ACCESS = 0x37F,

        /// <summary>Required to use the clipboard.</summary>
        WINSTA_ACCESSCLIPBOARD = 0x0004,

        /// <summary>Required to manipulate global atoms.</summary>
        WINSTA_ACCESSGLOBALATOMS = 0x0020,

        /// <summary>Required to create new desktop objects on the window station.</summary>
        WINSTA_CREATEDESKTOP = 0x0008,

        /// <summary>Required to enumerate existing desktop objects.</summary>
        WINSTA_ENUMDESKTOPS = 0x0001,

        /// <summary>Required for the window station to be enumerated.</summary>
        WINSTA_ENUMERATE = 0x0100,

        /// <summary>Required to successfully call the ExitWindows or ExitWindowsEx function. Window stations can be shared by users and this access type can prevent other users of a window station from logging off the window station owner.</summary>
        WINSTA_EXITWINDOWS = 0x0040,

        /// <summary>Required to read the attributes of a window station object. This attribute includes color settings and other global window station properties.</summary>
        WINSTA_READATTRIBUTES = 0x0002,

        /// <summary>Required to access screen contents.</summary>
        WINSTA_READSCREEN = 0x0200,

        /// <summary>Required to modify the attributes of a window station object. The attributes include color settings and other global window station properties.</summary>
        WINSTA_WRITEATTRIBUTES = 0x0010,
    }

    /// <summary>
    /// OpenDesktop 2nd param
    /// </summary>
    public enum OpenDesktopFlag : uint
    {
        /// <summary>
        /// Default value
        /// </summary>
        DF_NONE = 0x0000,

        /// <summary>
        /// Allows processes running in other accounts on the desktop to set hooks in this process.
        /// </summary>
        DF_ALLOWOTHERACCOUNTHOOK = 0x0001,
    }

    /// <summary>
    /// REF MSDN:Desktop Security and Access Rights
    /// ms-help://MS.MSDN.vAug06.en/dllproc/base/desktop_security_and_access_rights.htm
    /// </summary>
    [FlagsAttribute]
    public enum DesktopAccessRight : uint
    {
        /// <summary>Required to create a menu on the desktop. </summary>
        DESKTOP_CREATEMENU = 0x0004,

        /// <summary>Required to create a window on the desktop. </summary>
        DESKTOP_CREATEWINDOW = 0x0002,

        /// <summary>Required for the desktop to be enumerated. </summary>
        DESKTOP_ENUMERATE = 0x0040,

        /// <summary>Required to establish any of the window hooks. </summary>
        DESKTOP_HOOKCONTROL = 0x0008,

        /// <summary>Required to perform journal playback on a desktop. </summary>
        DESKTOP_JOURNALPLAYBACK = 0x0020,

        /// <summary>Required to perform journal recording on a desktop. </summary>
        DESKTOP_JOURNALRECORD = 0x0010,

        /// <summary>Required to read objects on the desktop. </summary>
        DESKTOP_READOBJECTS = 0x0001,

        /// <summary>Required to activate the desktop using the SwitchDesktop function. </summary>
        DESKTOP_SWITCHDESKTOP = 0x0100,

        /// <summary>Required to write objects on the desktop. </summary>
        DESKTOP_WRITEOBJECTS = 0x0080,
    }
}