How to UAC elevate a COM component with .NET

Question

I've found an article on how to elevate a COM object written in C++ by calling CoCreateInstanceAsAdmin. But what I have not been able to find or do, is a way to implement a component of my .NET (c#) application as a COM object and then call into that object to execute the tasks which need UAC elevation. MSDN documents this as the admin COM object model.

I am aware that it is possible and quite easy to launch the application (or another app) as an administrator, to execute the tasks in a separate process (see for instance the post from Daniel Moth, but what I am looking for is a way to do everything from within the same, un-elevated .NET executable. Doing so will, of course, spawn the COM object in a new process, but thanks to transparent marshalling, the caller of the .NET COM object should not be (too much) aware of it.

Any ideas as to how I could instanciate a COM object written in C#, from a C# project, through the CoCreateInstanceAsAdmin API would be very helpful. So I am really interested in learning how to write a COM object in C#, which I can then invoke from C# through the COM elevation APIs.

Never mind if the elevated COM object does not run in the same process. I just don't want to have to launch the whole application elevated; I would just like to have the COM object which will execute the code be elevated. If I could write something along the lines:

// in a dedicated assembly, marked with the following attributes:
[assembly: ComVisible (true)]
[assembly: Guid ("....")]

public class ElevatedClass
{
    public void X() { /* do something */ }
}

and then have my main application just instanciate ElevatedClass through the CoCreateInstanceAsAdmin call. But maybe I am just dreaming.

Answer 1

Look at Windows Vista UAC Demo Sample Code

(You also need the Vista Bridge sample for UnsafeNativeMethods.CoGetObject method)

Which gives you C# code that shows a few different ways to elevate, including a COM object

(Incomplete code sample - grab the files above)

[return: MarshalAs(UnmanagedType.Interface)]
static internal object LaunchElevatedCOMObject(Guid Clsid, Guid InterfaceID)
   {
   string CLSID = Clsid.ToString("B"); // B formatting directive: returns {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} 
   string monikerName = "Elevation:Administrator!new:" + CLSID;

   NativeMethods.BIND_OPTS3 bo = new NativeMethods.BIND_OPTS3();
   bo.cbStruct = (uint)Marshal.SizeOf(bo);
   bo.hwnd = IntPtr.Zero;
   bo.dwClassContext = (int)NativeMethods.CLSCTX.CLSCTX_ALL;

   object retVal = UnsafeNativeMethods.CoGetObject(monikerName, ref bo, InterfaceID);

   return (retVal);
}