How to enumerate the COM Object Members like interfaces, properties and methods

comwinapi

Which WinAPI method or interface I can use to enumerate the interfaces, properties, methods(and parameters) of a COM Object programmatically?

Best Answer

You need to be more specific. There are two ways to interpret your question.

One is that you have a COM component (e.g. some library), and you want to programmatically enumerate interfaces/properties/methods of that. Usually (but not always), COM components come with a type library that contains full metainformation about all this - it's either embedded into the COM .exe or .dll, or is a separate .tlb file. In any case, if the COM component is properly registered in the system (e.g. using regsvr32), then COM provides a standard API to retrieve that type information, centered around ITypeLib and ITypeInfo interfaces.

Another interpretation is that you get a reference to a particular COM object, and you need to enumerate all methods/properties on that and/or invoke them by computed name, like Java or C# reflection, or Delphi RTTI. If so, then it is only possible if the COM object implements IDispatch interface, which allows you to do all of the above.

Related Solutions

C# – How does the C# compiler detect COM types

By no means am I an expert in this, but I stumbled recently on what I think you want: the CoClass attribute class.

[System.Runtime.InteropServices.CoClass(typeof(Test))]
public interface Dummy { }

A coclass supplies concrete implementation(s) of one or more interfaces. In COM, such concrete implementations can be written in any programming language that supports COM component development, e.g. Delphi, C++, Visual Basic, etc.

See my answer to a similar question about the Microsoft Speech API, where you're able to "instantiate" the interface SpVoice (but really, you're instantiating SPVoiceClass).

[CoClass(typeof(SpVoiceClass))]
public interface SpVoice : ISpeechVoice, _ISpeechVoiceEvents_Event { }

Windows – How to detect all interfaces a COM object implements

You can try IDispatch/IDispatchEx if you simply want to know what methods are callable from your consumer.

In COM, the QueryInterface method on IUnknown is not required to expose what interfaces it may return. You ask for one based on its IID and you either get it or not. The implementation of QI in a particular COM object varies considerably although it's supposed to follow the pattern described by Microsoft here - http://msdn.microsoft.com/en-us/library/ms682521%28VS.85%29.aspx.

Best Answer

Related Solutions

C# – How does the C# compiler detect COM types

Windows – How to detect all interfaces a COM object implements

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