How to pass this struct array to unmanaged code?

Question

c# struct defined as:

[StructLayout(LayoutKind.Sequential)]
    public struct RecognizeResult
    {
        /// float
        public float similarity;

        /// char*
        [MarshalAs(UnmanagedType.LPStr)]
        public string fileName;
    }

c function signature:
void FaceRecognition(RecognizeResult *similarity); //where similarity is a pointer to an array

P/Invoke signature:

 [DllImport(DllName, EntryPoint = "FaceRecognition")]
   public static extern void Recognize(ref RecognizeResult similarity);

this is how i call the c++ function in managed code:

RecognizeResult[] results = new RecognizeResult[100];
Recognize(ref results[0]); //through p/invoke

it turns out the array can't be passed to unmanaged code, only the first element is passed. how should i do to pass an array to unmanaged code (is it even possible)?

BTW, Do i have to pin the array when calling unmanaged code so that GC won't move the array?

Answer 1

Try this:

[DllImport(DllName, EntryPoint = "FaceRecognition")]
public static extern void Recognize(RecognizeResult[] similarity);

RecognizeResult[] results = new RecognizeResult[100];
// fill array elements
Recognize(results);