LQ2

using System;
using System.Collections.Generic;
using System.Linq;
using System.Drawing;

namespace ClassWork
{
    internal class Program
    {
        public static void Main(string[] args)
        {
            var points = new Point[] { new Point(0, 0), new Point(0, 1) };
            foreach (var point in SecondTask(points))
                Console.WriteLine(point);
        }

        public static Point[] SecondTask(IEnumerable<Point> points)
        {
            return points
                .SelectMany(point =>
                {
                    var newPoints = new List<Point>();
                    for (int i = -1; i <= 1; i++)
                    {
                        for (int j = -1; j <= 1; j++)
                        {
                            newPoints.Add(new Point(point.X + i, point.Y + j));
                        }
                    }
                    return newPoints;
                })
                .Distinct()
                .ToArray();
        }
    }
}