Declaring COM interface pointer without header file

Question

I am writing an application using C# and WinForms. I have an ActiveX control provided by a third party. I drag the ActiveX control to a form, and get an instance of the class (call it "Widget") that the control implements.

Now I need to pass an interface pointer, IWidget, from C# into legacy C++ code. I plan to put the C++ code in a dll and call it from C# using P/Invoke. The problem is I don't know how to provide the IWidget definition to the C++ code. The original authors of the C++ code had header files (say widget.h), so they could #include widget.h, and declare an IWidget pointer.

I don't have the .h (and can't get it). I only have the ActiveX. So how can I declare an IWidget pointer in my dll?

My only idea so far is to create an IDL file from the ActiveX dll. Is that a reasonable approach?

Thanks, Mark

Use the #import directive. http://msdn.microsoft.com/en-us/library/8etzzkb6%28v=VS.90%29.aspx — Hans Passant, Dec 20 '11 at 17:04
Does the IDL have a definition for IWidget? Post that and you should be able to get the C# equivalent. — D Stanley, Dec 20 '11 at 17:09
#import looks promising. I will try that when I get a chance in a couple days. Thank you everyone for the responses. — Mark Schmucker, Dec 20 '11 at 21:59
#import worked great. Hans, if you care to post your comment as an answer, I will accept it. — Mark Schmucker, Dec 21 '11 at 17:21

score 0 · Answer 1 · edited May 23 '17 at 11:55

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You can try import metadata from ActiveX with tlbimp.exe which create managed assembly and IWidget should be there. If you create class with this managed version of interface and [ClassInterface(ClassInterfaceType.AutoDispatch)], it should pass through to ActiveX.

See howto for tlbimp activex-wrap

edited May 23 '17 at 11:55

Community

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answered Dec 20 '11 at 19:18

Radik

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Declaring COM interface pointer without header file

1 Answers1