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I wrote a class that implements the IGroupPolicyObject Interface in COM. one of the method now returns IntPtr object in C#:

IntPtr ghKey = objectGPolicy.GetRegistryKey(GpoSectionMachine);

I want to derefrence that pointer when using the RegistryKey object that belongs to Microsot.Win32 namespace.

This DOESN'T work:

(RegistryKey)ghKey = rootKey.CreateSubKey(policyPath);

I can't find how to derefrence an IntPtr. Can someone help please?

Thanks

Saher Ahwal
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1 Answers1

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IGroupPolicyObject.GetRegistryKey doesn't return a .NET RegistryKey object, it returns a Win32 registry key handle (an HKEY). There are two useful things you can do with an IntPtr value that contains a native HKEY. First, you can pass it to other Win32 registry access functions. If you use it this way, you also need to manually close it by calling RegCloseKey when you're done, or it will leak the handle.

As @HansPassant helpfully points out in his comment, your second (and probably better) option is to turn it into a SafeRegistryHandle and use it to get a RegistryKey object:

var hkey = gpo.GetRegistryKey(GpoSectionMachine);
var safeHandle = new SafeRegistryHandle(hkey, true);
var reg = RegistryKey.FromHandle(safeHandle);

If you wrote a managed implementation of IGroupPolicyObject and it returns an actual RegistryKey object from this function, then:

  1. You did it wrong and your implementation is not portable to any other consumer of IGroupPolicyObject, and
  2. You must have manually marshalled your RegistryKey object into an IntPtr in your implementation, so just do the opposite to get it back out. (But really -- don't do that, you are breaking the COM contract by returning the wrong type.)

An implementation of this method should instead be written to return a SafeRegistryHandle (the marshaler will, I believe, automatically convert between SafeHandle and an unmanaged handle). RegistryKey.Handle is one of these so you can use the C# classes right up until you need to return something from your implementation.

Michael Edenfield
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  • from the GetRegistryKey Function my managed implementation returns IntPtr value. Can you give an example of how can I use that IntPtr with the registry access functions in C#? Thanks – Saher Ahwal Jun 15 '12 at 03:01
  • The Win32 registry access functions all take an HKEY value, which is translated into C# as an IntPtr. Assuming that your GetRegistryKey function is returning a valid HKEY as an IntPtr you just pass that value directly back to, say RegQueryValueEx. – Michael Edenfield Jun 15 '12 at 03:04
  • but the RegQueryValueEx is C++ not C#. that's the whole point I want C#. – Saher Ahwal Jun 15 '12 at 03:54
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    RegQueryValueEx is Win32, not "C++", you call it from C# using P/Invoke. But see my edits: there is a way to stay in managed code by shifting between `IntPtr` and a `SafeRegistryHandle` as needed. – Michael Edenfield Jun 15 '12 at 13:51
  • Thank You. I ended up using Interops with DllImport. – Saher Ahwal Jun 15 '12 at 21:20