PInvoke Issues...

From: Richard (Richard_at_discussions.microsoft.com)
Date: 08/10/04 

Date: Tue, 10 Aug 2004 11:39:02 -0700

Hi,

I want to programmatically open a service and tune it's configuration from
C#. I think I'm having PInvoke issues because I imported the service API
functions and I'm getting nonsense errors from GetLastError() {RPC server not
found/file volume label incorrect} when I try to open the SCM database. I'm
trying to open it on my local machine and I am an Administrator... Questions:

Here's the WIN32 API signature that I'm getting nonsense errors from:

SC_HANDLE OpenSCManager(
  LPCTSTR lpMachineName,
  LPCTSTR lpDatabaseName,
  DWORD dwDesiredAccess
);

Does the code below look like I imported it correctly? I am marshalling the
strings and the DWORD correctly - yes? Do I have to do anyhting special if I
want to marshal the strings as const? What's the PInvoke way to pass a NULL
string to this WIN32 API? I would like to pass nulls for the strings as the
API documentation says this function defaults to the correct settings for my
needs...

[DllImport("AdvApi32.dll", SetLastError = true)]
static extern IntPtr OpenSCManager([MarshalAs(UnmanagedType.LPTStr)] string
machineName, [MarshalAs(UnmanagedType.LPTStr)] string databaseName, uint
desiredAccess);

I'm calling the function like this:

managerHandle = OpenSCManager(null, SERVICES_ACTIVE_DATABASE, (uint)
ServiceAccess.SC_MANAGER_ENUMERATE_SERVICE);
uint error = GetLastError();

Depending on what I pass for my machine name {tried Environment.MachineName
with no luck} I get bizarre error return code back and the handle may or may
not be 0. If the handle is not 0 and I try to use it I always get an
"invalid handle" error...

Any help would be appreciated...

--Richard

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