Question

I have c++ dll with class in wich I want to send string from C# code, surly I can’t use string because of CLR, i’ll stried to change string into char in c++ dll, and send byte from c#(because c++ char=byte in c#) but c# don’t understand c++ array I can send 1 byte and it will be ok, but not array, please help!
dll Code:

public ref class Coding
    {
    public:
        void HillCoding(char filePath[])
        {

            ...
        }
    };

Answer 1

Here is the working code of calling C++ dll function from C#:

    sbyte[] A_SB_array = new sbyte[0];
    ArrayConvCtoSB(ref A_SB_array, ar_param.ToCharArray());
    fixed (sbyte* SB_array = A_SB_array)
        return CPSFEW.getDataLength(SB_array);

It’s not the “very good code” but it illustrate what you need.

PS: Here is ArrayConvCtoSB. I do not like it, it’s just for understanding.

    static private void ArrayConvCtoSB(ref sbyte[] to_sbyte, char[] from_char)
    {
        for (int i = 0; i < from_char.Length; i++)
        {
            Array.Resize(ref to_sbyte, to_sbyte.Length + 1);
            to_sbyte[i] = (sbyte)from_char[i];
        }
    }

PPS: “fixed” is strongly required for forceing garbage collector not to clear the SB_array memory: otherwise it can. 🙂