Question

I have such construction

List<int[]> propIDs = new List<int[]>();

Can I get all unique value from propIDs with LINQ.For example I have list of
(1,2)
(4,5)
(1,5)
(1,2)
(1,5)
and I must get
(1,2)
(4,5)
(1,5)

Answer 1

Below is a complete and working application of your need.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ListsAndArrays
{
    class Program
    {
        static void Main(string[] args)
        {
            List<int[]> propIDs = new List<int[]>();
            propIDs.Add(new[] { 1, 2 });
            propIDs.Add(new[] { 4, 5 });
            propIDs.Add(new[] { 1, 5 });
            propIDs.Add(new[] { 1, 2 });
            propIDs.Add(new[] { 1, 5 });

            var distinct = propIDs.Distinct(new DistinctIntegerArrayComparer());

            foreach (var item in distinct)
            {
                Console.WriteLine("{0}|{1}", item[0], item[1]);
            }

            if (Debugger.IsAttached)
            {
                Console.ReadLine();
            }
        }

        private class DistinctIntegerArrayComparer : IEqualityComparer<int[]>
        {
            public bool Equals(int[] x, int[] y)
            {
                if (x.Length != y.Length) { return false; }
                else if (x.Length != 2 || y.Length != 2) { return false; }

                return x[0] == y[0] && x[1] == y[1];
            }

            public int GetHashCode(int[] obj)
            {
                return -1;
            }
        }

    }
}