Re: Marshalling C# Strings to VC++ =?UTF-8?B?Ni4w4oCP4oCP?=

We had similar porting issues when we put together our .NET API.

What was a big helper was the

        Microsoft P/Invoke Interop Assistant utility

that translate C/C++ prototypes code to .NET code for C# or VB.

You have to download it. I think from here:

http://clrinterop.codeplex.com/releases/view/14120
http://clrinterop.codeplex.com/Wikipage
http://channel9.msdn.com/posts/funkyonex/The-P-Invoke-Interop-Assistant/

If you want a rich set of examples of C/C++ structures and 250+ API
ported to a .NET interface which I also compiled into a .NET COM
interface, see

      http://www.winserver.com/public/wcsdk

To maybe save you time that I wasted, I spent a lot of time thinking I
had to do my own marshaling coding with .NET class wrappers, but it
turned out that was just getting the prototyping and delegates right
worked most of the time.

But if I recall one of the issue with many of the functions is that
VARIANTS are not supported out of the box (BSTR is a variant) or I
didn't figure it out.

However, since we already had a C/C++ proxy DLL that does BSTR
variants interfacing for Classic VB and COM API support, using this
proxy (WCVB.DLL) for some of the functions in .NET API) this turned
out easier than trying to use some 3rd party .NET variant class I had
found. I don't recall if I could of used the iMarshalling stuff or I
tried or not, but it was just easily to use the C/C++ to BSTR proxy
DLL we already had.

For example, most of the API use our WIN32 DLL wcsrv2.dll, but for
some other functions we use the proxy WCVB.DLL.

Example:

The ported function in .NET

[DllImport("wcvb.dll",
            EntryPoint="vbWcGetPrivateProfileString",
            SetLastError=true)]
   public extern static string WcGetPrivateProfileString(
        string section,
        string key,
        string def,
        string ini);

the pure WIN32 function is in wcserver.h header for WCSRV2.DLL

BOOL APIENTRY WcGetPrivateProfileString
                   (const char *sect,
                    const char *key,
                    const char *defvalue,
                    char *dest,
                    DWORD *destsize,
                    const char *inifile);

Since this returns as a parameter an asciiz string, it doesn't lend
itself to COM and .NET. It is better to have it return a string to
avoid any marshaling conversion code on your own. So a 2nd DLL
provides a VARIANT version wrapper function for the above C WIN32
function:

BSTR APIENTRY vbWcGetPrivateProfileString
                   (const char *sect,
                    const char *key,
                    const char *defvalue,
                    const char *inifile)
{
     char *dest = NULL;
     DWORD size = 0;
     while (1) {
         size += 1024;
         dest = new CHAR[size];
         if
(WcGetPrivateProfileString(sect,key,defvalue,dest,&size,inifile)) {
             break;
         }
         if (GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
            delete dest;
            return NULL;
         }
     }
     BSTR result = SysAllocStringLen((OLECHAR *)dest, (strlen(dest)+1)/2);
     delete dest;
     return result;
}

Hope the above gives you stuff things to look at.

--

Scott Ballard wrote:


--
HLS