将C＃字节[]传递给C ++ API

Question

I have to pass an Byte array containing an MAC-Address to a C++ Method. Since I don't have much experience with working with c C++ APIsI don't know how to do this. I've tried to pass the array itself, but got an invalid parameter code as response from the API . I've also tried to create an IntPtr but to no avail.
I know that the problem is that C++ can't handle managed datatypes such as arrays, so I've to create a unmanaged array somehow, I think.

Here is the definition of the C++ Method:

ll_status_t LL_Connect(
ll_intf_t intf, 
uint8_t address[6]);

The array in C# is defined the following way:

Byte[] addr = new Byte[6];

Of course, the array is not empty.

Answer 1

For example:

C++

extern "C"
{
    __declspec(dllexport) void GetData(uint8_t* data, uint32_t length)
    {
      for (size_t i = 0; i < length; ++i)
        data[i] = i;
    }
}

C#

[DllImport("LibName.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
public static extern void GetData([In, Out] [MarshalAs(UnmanagedType.LPArray)] byte[] data, uint length);

And use in C#

 byte[] data = new byte[4];
 GetData(data, (unit)data.Lenght);

If you have an array fixed length, for example:

C++

extern "C"
{
    __declspec(dllexport) void GetData(uint8_t data[6])
    {
      for (size_t i = 0; i < 6; ++i)
        data[i] = i;
    }
}

C#

[DllImport("LibName.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
public static extern void GetData([In, Out] [MarshalAs(UnmanagedType.LPArray, SizeConst = 6)] byte[] data);

And use in C#

 byte[] data = new byte[6];
 GetData(data);

For your case:

    [DllImport("LibName.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
    public static extern int LL_Connect(byte intf, [In, Out] [MarshalAs(UnmanagedType.LPArray, SizeConst = 6)] byte[] address);