Problem : Getting a mobile drive size using C# throws exception - Commented

CONADefinitions.CONAPI_FOLDER_INFO2 FolderInfo;
int iResult = 0;
IntPtr Buffer =  Marshal.AllocHGlobal(Marshal.SizeOf(typeof(CONADefinitions.CONAPI_FOLDER_INFO2)));
iResult = CONAFileSystem.CONAFindNextFolder(hFindHandle, Buffer);
while (iResult == PCCSErrors.CONA_OK )
{
 FolderInfo = (CONADefinitions.CONAPI_FOLDER_INFO2)Marshal.PtrToStructure(Buffer,typeof(CONADefinitions.CONAPI_FOLDER_INFO2));
    //......................... i got an error msg here as follows:
    // Error Messege:
       FatalExecutionEngineError was detected Message: The runtime has encountered a
       fatal error. The address of the error was at 0x7a0ba769, on thread 0x1294. The
       error code is 0xc0000005. This error may be a bug in the CLR or in the unsafe
       or non-verifiable portions of user code. Common sources of this bug include
       user marshaling errors for COM-interop or PInvoke, which may corrupt the stack.

DriveInfo di = new DriveInfo("f");  //Put your mobile drive name
        long totalBytes = di.TotalSize;
        long freeBytes = di.TotalFreeSpace;