Creates a process as a user in a untrusted domain

CreateProcessAsUser.cs

public void CreateProcessAsUser(string applicationName, string commandLine, string username, string domainName, string password)
{
    var si = new STARTUPINFO();
    var pi = new PROCESS_INFORMATION();
    if (!CreateProcessWithLogonW(username, domainName, password,
        LogonFlags.LOGON_NETCREDENTIALS_ONLY, null, applicationName + " " + commandLine,
        CreationFlags.CREATE_DEFAULT_ERROR_MODE, 0, null, ref si, out pi))
    {
        throw new Win32Exception();
    }

    WaitForSingleObject(pi.hProcess, 0xffffffff);

    CloseHandle(pi.hProcess);
    CloseHandle(pi.hThread);
}

[DllImport("kernel32.dll", SetLastError = true)]
static extern UInt32 WaitForSingleObject(IntPtr hHandle, UInt32 dwMilliseconds);

[DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
private static extern bool CreateProcessWithLogonW(
    String userName,
    String domain,
    String password,
    LogonFlags logonFlags,
    String applicationName,
    String commandLine,
    CreationFlags creationFlags,
    UInt32 environment,
    String currentDirectory,
    ref STARTUPINFO startupInfo,
    out PROCESS_INFORMATION processInformation);

[DllImport("kernel32.dll", SetLastError = true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
[SuppressUnmanagedCodeSecurity]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool CloseHandle(IntPtr hObject);

[Flags]
enum CreationFlags
{
    CREATE_SUSPENDED = 0x00000004,
    CREATE_NEW_CONSOLE = 0x00000010,
    CREATE_NEW_PROCESS_GROUP = 0x00000200,
    CREATE_UNICODE_ENVIRONMENT = 0x00000400,
    CREATE_SEPARATE_WOW_VDM = 0x00000800,
    CREATE_DEFAULT_ERROR_MODE = 0x04000000,
}

[Flags]
enum LogonFlags
{
    LOGON_WITH_PROFILE = 0x00000001,
    LOGON_NETCREDENTIALS_ONLY = 0x00000002
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
private 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 dwYSize;
    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)]
private struct PROCESS_INFORMATION
{
    public IntPtr hProcess;
    public IntPtr hThread;
    public int dwProcessId;
    public int dwThreadId;
}