public static IntPtr WTS_CURRENT_SERVER_HANDLE = IntPtr.Zero;

public static void ShowMessageBox(string message, string title)
{
int resp = 0;
WTSSendMessage(
WTS_CURRENT_SERVER_HANDLE,
WTSGetActiveConsoleSessionId(),
title, title.Length,
message, message.Length,
0, 0, out resp, false);
}

[DllImport("kernel32.dll", SetLastError = true)]
public static extern int WTSGetActiveConsoleSessionId();

[DllImport("wtsapi32.dll", SetLastError = true)]
public static extern bool WTSSendMessage(
IntPtr hServer,
int SessionId,
String pTitle,
int TitleLength,
String pMessage,
int MessageLength,
int Style,
int Timeout,
out int pResponse,
bool bWait);

protected override void OnStart(string[] args)
{
Interop.ShowMessageBox("This a message from AlertService.", "AlertService Message");
}

public static void CreateProcess(string app, string path)
{
bool result;
IntPtr hToken = WindowsIdentity.GetCurrent().Token;
IntPtr hDupedToken = IntPtr.Zero;

PROCESS_INFORMATION pi = new PROCESS_INFORMATION();
SECURITY_ATTRIBUTES sa = new SECURITY_ATTRIBUTES();
sa.Length = Marshal.SizeOf(sa);

STARTUPINFO si = new STARTUPINFO();
si.cb = Marshal.SizeOf(si);

int dwSessionID = WTSGetActiveConsoleSessionId();
result = WTSQueryUserToken(dwSessionID, out hToken);

if (!result)
{
ShowMessageBox("WTSQueryUserToken failed", "AlertService Message");
}

result = DuplicateTokenEx(
hToken,
GENERIC_ALL_ACCESS,
ref sa,
(int)SECURITY_IMPERSONATION_LEVEL.SecurityIdentification,
(int)TOKEN_TYPE.TokenPrimary,
ref hDupedToken
);

if (!result)
{
ShowMessageBox("DuplicateTokenEx failed" ,"AlertService Message");
}

IntPtr lpEnvironment = IntPtr.Zero;
result = CreateEnvironmentBlock(out lpEnvironment, hDupedToken, false);

if (!result)
{
ShowMessageBox("CreateEnvironmentBlock failed", "AlertService Message");
}

result = CreateProcessAsUser(
hDupedToken,
app,
String.Empty,
ref sa, ref sa,
false, 0, IntPtr.Zero,
path, ref si, ref pi);

if (!result)
{
int error = Marshal.GetLastWin32Error();
string message = String.Format("CreateProcessAsUser Error: {0}", error);
ShowMessageBox(message, "AlertService Message");
}

if (pi.hProcess != IntPtr.Zero)
CloseHandle(pi.hProcess);
if (pi.hThread != IntPtr.Zero)
CloseHandle(pi.hThread);
if (hDupedToken != IntPtr.Zero)
CloseHandle(hDupedToken);
}

[StructLayout(LayoutKind.Sequential)]
public struct STARTUPINFO
{
public Int32 cb;
public string lpReserved;
public string lpDesktop;
public string lpTitle;
public Int32 dwX;
public Int32 dwY;
public Int32 dwXSize;
public Int32 dwXCountChars;
public Int32 dwYCountChars;
public Int32 dwFillAttribute;
public Int32 dwFlags;
public Int16 wShowWindow;
public Int16 cbReserved2;
public IntPtr lpReserved2;
public IntPtr hStdInput;
public IntPtr hStdOutput;
public IntPtr hStdError;
}

[StructLayout(LayoutKind.Sequential)]
public struct PROCESS_INFORMATION
{
public IntPtr hProcess;
public IntPtr hThread;
public Int32 dwProcessID;
public Int32 dwThreadID;
}

[StructLayout(LayoutKind.Sequential)]
public struct SECURITY_ATTRIBUTES
{
public Int32 Length;
public IntPtr lpSecurityDescriptor;
public bool bInheritHandle;
}

public enum SECURITY_IMPERSONATION_LEVEL
{
SecurityAnonymous,
SecurityIdentification,
SecurityImpersonation,
SecurityDelegation
}

public enum TOKEN_TYPE
{
TokenPrimary = 1,
TokenImpersonation
}

public const int GENERIC_ALL_ACCESS = 0x10000000;

[DllImport("kernel32.dll", SetLastError = true,
CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
public static extern bool CloseHandle(IntPtr handle);

[DllImport("advapi32.dll", SetLastError = true,
CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall)]
public static extern bool CreateProcessAsUser(
IntPtr hToken,
string lpApplicationName,
string lpCommandLine,
ref SECURITY_ATTRIBUTES lpProcessAttributes,
ref SECURITY_ATTRIBUTES lpThreadAttributes,
bool bInheritHandle,
Int32 dwCreationFlags,
IntPtr lpEnvrionment,
string lpCurrentDirectory,
ref STARTUPINFO lpStartupInfo,
ref PROCESS_INFORMATION lpProcessInformation);

[DllImport("advapi32.dll", SetLastError = true)]
public static extern bool DuplicateTokenEx(
IntPtr hExistingToken,
Int32 dwDesiredAccess,
ref SECURITY_ATTRIBUTES lpThreadAttributes,
Int32 ImpersonationLevel,
Int32 dwTokenType,
ref IntPtr phNewToken);

[DllImport("wtsapi32.dll", SetLastError=true)]
public static extern bool WTSQueryUserToken(
Int32 sessionId,
out IntPtr Token);

[DllImport("userenv.dll", SetLastError = true)]
static extern bool CreateEnvironmentBlock(
out IntPtr lpEnvironment,
IntPtr hToken,
bool bInherit);

protected override void OnStart(string[] args)
{
Interop.CreateProcess("cmd.exe",@"C:\Windows\System32\");
}