Passing a managed (C#) string[] array to a COM DLL

Question

Setup:
I have a COM DLL that calls a method inside a managed C# DLL. This function returns a C# string[] array, which is marshaled to a SAFEARRAY.

Problem:
When I try to access the strings within the safearray I only get the first char of the string. What am I doing wrong?

The code:

    // Pointer to the managed interface
    DatabasePtr pODB(__uuidof(DBClass));

    // Get the string[] array from the managed method
    SAFEARRAY* safearray = pODB->GetStringArray();

    HRESULT hresult;

    long ubound;
    long lbound;

    hresult = SafeArrayGetUBound(safearray, 1, &ubound);
    hresult = SafeArrayGetLBound(safearray, 1, &lbound);

    long index;
    BSTR fromarray;

    for (; lbound <= ubound; lbound++)
    {
        index = lbound;

        hresult = SafeArrayGetElement(safearray, &index, (void*)&fromarray);

        char buffer[512];
        sprintf_s(buffer,"%s",fromarray);

        MessageBox(0, (LPCSTR)buffer, "...", 0);
    }

Thanks for your help,
-Sean!

Answer 1

The BSTR is an unicode string, so you must use an wchar_t buffer and the wsprintf_s. Right now u print the ANSI part of the first unicode character then stop on the \0. And please, please, don't stack overflow like that (sic!). Use the safe _vsnwprintf_s_l and its family, your code is a hacker's delight as it is right now and u'll be pwned. See http://msdn.microsoft.com/en-us/library/d3xd30zz(VS.80).aspx