using System;

using System.Collections.Generic;

using System.Linq;

​

public static class ArrayExtensions

{

    public static IEnumerable<int> StartingIndex(this byte[] x, byte[] y)

    {

        IEnumerable<int> index = Enumerable.Range(0, x.Length - y.Length + 1);

​

        for (int i = 0; i < y.Length; i++)

        {

            index = index.Where(n => x[n + i] == y[i]).ToArray();

        }

​

        return index;

    }

}

​

public class Program

{

    static void Main(string[] args)

    {

        byte[] x = new byte[] { 1, 2, 3, 3, 3, 6, 3, 3, 3 };

        byte[] y = new byte[] { 3, 3 };

        int[] expected = new int[] { 2, 6 };

​

        IEnumerable<int> result = x.StartingIndex(y);

​

        Console.WriteLine("Result: " + string.Join(", ", result));

​

        Console.WriteLine("Expected: " + string.Join(", ", expected));

        Console.WriteLine("Result matches expected: " + Enumerable.SequenceEqual(result, expected));

    }

}