Pass byte array from C# to C++ and vice-versa

Pass byte array from C# to C++                          

If you want to pass a byte array to native DLL as parameter, you can use the Intptr to do this, please check the demo below.

/C++ API code:
TestDLL_API  void TestArrayPara(BYTE * pArray, int nSize)
{
        for (int i=0; i<nSize; i++)
        printf("%d\n", pArray[i]);
}

//C# code:
class TestClass
    {
        [DllImport(@"TestDll.dll")]
        public static extern void TestArrayPara(IntPtr pArray, int nSize);
        public static void Test()
        {
            byte[] array = new byte[16];
             for (int i = 0; i < 16; i++)
            {
                array[i] = (byte)(i + 97);
            }
            int size = Marshal.SizeOf(array[0]) * array.Length;
            IntPtr pnt = Marshal.AllocHGlobal(size);
           try
            {
                // Copy the array to unmanaged memory.
                Marshal.Copy(array, 0, pnt, array.Length);               
            }
            finally
            {
                // Free the unmanaged memory.
               // Marshal.FreeHGlobal(pnt);
            }
            TestArrayPara(pnt, array.Length);
            Marshal.FreeHGlobal(pnt);
            Console.WriteLine("End of app");
        }
}


Return char array from C++ to c#


//C++ code
extern "C" __declspec(dllexport) int* test() 
{
    int * arr=new int[4];
    arr[0]=1;
    arr[1]=2;
    arr[2]=3;
    arr[3]=4;
        return arr;}

extern "C" __declspec(dllexport) int ReleaseMemory(int* pArray){
    delete[] pArray;
    return 0;}


//C# code
[DllImport("C:\\Devs\\C++\\Projects\\Interop\\InteropTestApp\\Debug\\InteropTestApp.dll")]
        public static extern IntPtr test();

        [DllImport("C:\\Devs\\C++\\Projects\\Interop\\InteropTestApp\\Debug\\InteropTestApp.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int ReleaseMemory(IntPtr ptr);
        static void Main(string[] args)
        {
            IntPtr ptr = test();
            int[] result = new int[4];
            Marshal.Copy(ptr, result, 0, 4);
            ReleaseMemory(ptr);
            Console.ReadKey();
        }


    }