3rd party dll interface to c++/cli .net 2.x

[microface]

Yes I have googled, and found lots of supposed answers to this problem of using P/Invoke but everything I found, and everything I tried either caused exceptions, or simply failed to fill in the struct.
So here is my problem

typedef struct tagEdsDirectoryItemInfo
{
    EdsUInt32   size;
    EdsBool     isFolder;
    EdsUInt32   groupID;
    EdsUInt32   option;
    EdsChar     szFileName[ EDS_MAX_NAME ];

} EdsDirectoryItemInfo;

unsigned int EDSAPI EdsGetDirectoryItemInfo(
                                EdsDirectoryItemRef    inDirItemRef,
                                EdsDirectoryItemInfo*   outDirItemInfo );


 /*-----------------------------------------------------------------------------
         DirectoryItem Info
        -----------------------------------------------------------------------------*/
        [StructLayout(LayoutKind::Sequential)]
        value struct EdsDirectoryItemInfo 
        {
            unsigned int Size;
            int  isFolder;
            unsigned int GroupID;
            unsigned int Option;
            [MarshalAs(UnmanagedType::LPArray,SizeConst=EDS_MAX_NAME)]
            cli::array<char> ^szFileName;
            
            //[MarshalAs( UnmanagedType::ByValTStr, SizeConst=EDS_MAX_NAME)]
            //System::Text::StringBuilder ^  szFileName;
            //[MarshalAs(UnmanagedType::AsAny,SizeConst=EDS_MAX_NAME)]
            //cli::array<char> ^szFileName;
            //EdsDirectoryItemInfo():szFileName(gcnew cli::array<char>(EDS_MAX_NAME+1)){;};
            
        };

        [System::Runtime::InteropServices::DllImportAttribute("EDSDK.dll",CallingConvention = CallingConvention::Cdecl)]
        static  unsigned int EdsGetDirectoryItemInfo( IntPtr inDirItemRef,
             EdsDirectoryItemInfo^ outDirItemInfo);
//        static  unsigned int EdsGetDirectoryItemInfo( IntPtr inDirItemRef,
//             IntPtr outDirItemInfo);

I am calling this dll exported function in this Canon SDK from a delegate.
The delegate is called, and depending on what I do I can get exception from the 
marshalling, or err is 0 and nothing is filled in the outDirItemInfo

inRef is an IntPtr handle to some item in the 3rd party Canon SDK



Actual Function Calls
EdsDirectoryItemInfo^	dirItemInfo = gcnew EdsDirectoryItemInfo();
				dirItemInfo->szFileName = gcnew cli::array<char>EDS_MAX_NAME+1);
unsigned int err;
				
//IntPtr ptr;
//ptr = Marshal::AllocHGlobal(Marshal::SizeOf(dirItemInfo));

err = EdsGetDirectoryItemInfo( inRef,dirItemInfo);

I have tried many different types of marshalling, I have tried to make the dirItemInfo and IntPtr,
I am just very frustrated, after 3 days of futzing around with this I am just at the point of telling my boss it can not be done, and just write the code in gold old MFC.

Oh in the process the Canon SDK provided a C# class which was filled with errors that I had to fix, by looking at their C example.