PInvoke and IStream

I have an exported function from a dll written in c++ with the following signiture:

Foo( LPSTREAM *pStream, UINT &Size ) 

that returns an memory stream and obviously its size. What I am having difficulties with is creating a signiture for the exported function and then attempting to read the stream in C#. At one point was able to开发者_运维知识库 use "unsafe" byte pointer to get the information, but this does not fit our requirements.

Any thoughts, examples, samples etc would be greatly appreciated.

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You can do this like so:

[DLLImport(@"mydll.dll")]
public static extern void Foo(out ComTypes.IStream Stream, ref uint Size);

Call it like this:

ComTypes.IStream Stream = null;
uint Size;
Foo(out Stream, ref Size);

As normal, make sure your calling conventions match (C# defaults to stdcall, C++ defaults to cdecl).

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As an aside, why return the Size separate from the stream since IStream knows its size and will tell you if you ask it to?