I use old code with a c++/cli dll that does interact with UART.
Our main Application is programmed with c#.

Both the main c# Application as well as the c++/cli dll must access UART.

Because of that I tried to implement the read and write functions for UART in the c++/cli dll, sending seems to work but receiving does not. If I access the static Read function the Read Buffer always reads as 0 bytes in ComStat.cbInQue.

    static array<unsigned char>^ ComRead(short amount)
    {
        short read = ReadCommBlock(&ComDev, (char *)RecBuffer, amount);
        array<unsigned char>^ ComReceived = gcnew array<unsigned char>(read);
        for (int i = 0; i < read; i++)
        {
            ComReceived[i] = (unsigned char)RecBuffer[i];
        }
        return ComReceived;
    }

    int ReadCommBlock(HANDLE *pComDev, char * pBuffer, int MaxLength )
    {
        DWORD      Length;
        COMSTAT    ComStat    = {0};
        DWORD      ErrorFlags = 0;
        OVERLAPPED osRead     = {0,0,0};

        if (ErrorFlags != 0)
        {
            short breakpoint = 5;
        }

        /* only try to read number of bytes in queue */
        ClearCommError(*pComDev, &ErrorFlags, &ComStat);

        Length = min((DWORD)MaxLength, ComStat.cbInQue);
       
        if(Length > 0)
        {
            if(ReadFile(*pComDev, pBuffer, Length, &Length, &osRead) == FALSE)
            {
                Length = 0 ;

                ClearCommError(*pComDev, &ErrorFlags, &ComStat);

                assert(ErrorFlags == 0);
            }
        }
        else
        {
            Length = 0;
            Sleep(1);
        }

        return (Length);
    }    

I tried different methods to receive bytes via DLL