CODEWITHSUNDEEP
c++
Rahul
Rahul

Reputation: 39

Pass BSTR from C++ to C#

I have C# project "X" ,I have exposed methods in it to the C++ project "Y".

X has method signature as follows -

public void WriteInformation(string sInfo)
{
    m_logger.ErrorInfo("{0}", sInfo);
}

As I am exporting it to a C++ using .TLB file I checked declaration of this method in .tlh file which generates on #import of .tlb file.

virtual HRESULT __stdcall WriteInformation ( /*[in]*/ BSTR sMsg ) = 0;

I am calling this method in C++ project and passsing argument as follows - 

oLog->WriteInformation(BSTR("Info write successful"));

Issue here is the string passed from C++ always becomes garbage or null , I debugged it and I can see value of sInfo is always garbage or null.

Please let me know what method should be followed to pass string from C++ to C#.

Upvotes: 0

Views: 1571

Answers (2)

sharptooth
sharptooth

Reputation: 170499

You try to pass an ANSI string in place of BSTR. BSTR must be a wide character string. Also you shouldn't pass a string literal, you should properly allocate a BSTR using SysAllocString() (or better yet) a wrapper class like ATL::CComBSTR or _bstr_t. Btw _bstr_t has a constructor that will accept const char* and do the ANSI->UTF16 conversion for you.

Upvotes: 3

Sujay Ghosh
Sujay Ghosh

Reputation: 2868

I dont think its possible to interact with C++ and C# directly. I had interacted using a C++/CLI wrapper.

Upvotes: -1

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