Question

using System.Linq;

var a = new byte?[][,]{
    new byte?[,]{{1}},
    new byte?[,]{{1}},
    new byte?[,]{{2}},
    new byte?[,]{{1, 2, 3}, {4, 5, 6}}};
a = a.Distinct().ToArray();

However ‘a’ still contains a duplicate. Am I doing this correctly?

---

Thanks. From the information in the answers.

class Nullable_Byte_2D_Array_EqualityComparer : IEqualityComparer<byte?[,]>
{
    public bool Equals(byte?[,] a, byte?[,] b)
    {
        var r = a.GetLength(0) == b.GetLength(0) &&
            a.GetLength(1) == b.GetLength(1);
        if (r)
        {
            var v = new byte?[a.Length];
            byte n = 0;
            foreach (byte? c in a)
            {
                v[n] = c;
                n++;
            }
            n = 0;
            foreach (byte? c in b)
            {
                if (c != v[n])
                    r = false;
                n++;
            }
        }
        return r;
    }
}

And

a = a.Distinct(new Nullable_Byte_2D_Array_EqualityComparer()).ToArray();

Answer 1

It doesn’t contain a duplicate. It contains two distinct arrays which happen to have the same values inside of them. Since arrays are reference types, Distinct() does a reference comparison by default; to change this behavior, use this override to specify your own comparer.