Binary search, IComparer, in lambda expressions style , C#

Binary search, IComparer, in lambda expressions style

//http://stackoverflow.com/a/4870280/579026

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Collections.ObjectModel;
using System.Collections;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            List<TestClass> list = new List<TestClass>()
            {
                new TestClass() {SomeValue = 5},
                new TestClass() {SomeValue = 1},
                new TestClass() {SomeValue = 15},
                new TestClass() {SomeValue = -10},
                new TestClass() {SomeValue = 15},
                new TestClass() {SomeValue = 42},
                new TestClass() {SomeValue = 0}
            };
                
            list = list.OrderBy(f => f.SomeValue).ToList();
            Console.WriteLine(list.BinarySearch(new TestClass() {SomeValue = 15 }, new ValueComparer<TestClass>(f => f.SomeValue)));//note that it isn't the first match in the list
            
        }
        
        public class TestClass
        {
            public int SomeValue {get; set;}            
        }
    }
    
    //<summary>
    /// Contains all of the properties of a class that
    /// are used to provide value semantics.
    ///</summary>
    ///<remarks>
    /// You can create a static readonly ValueComparer for your class,
    /// then call into it from Equals, GetHashCode, and CompareTo.
    ///</remarks>
    class ValueComparer<T> : IComparer<T>, IEqualityComparer<T> 
    {
        public ValueComparer(params Func<T, object>[] props) 
        {
            Properties = new ReadOnlyCollection<Func<T, object>>(props);
        }
     
        public ReadOnlyCollection<Func<T, object>> Properties        
        { 
            get; 
            private set; 
        }
     
        public bool Equals(T x, T y) 
        {
            if (ReferenceEquals(x, y)) 
                return true;
            if (x == null || y == null) 
                return false;
            
            //Object.Equals handles strings and nulls correctly
            return Properties.All(f => Equals(f(x), f(y)));   
        }
     
        //http://stackoverflow.com/questions/263400/263416#263416
        public int GetHashCode(T obj) 
        {
            if (obj == null) return -42;
            unchecked 
            {
                int hash = 17;
                foreach (var prop in Properties) 
                {
                    object value = prop(obj);
                    if (value == null)
                        hash = hash * 23 - 1;
                    else
                        hash = hash * 23 + value.GetHashCode();
                }
                return hash;
            }
        }
     
        public int Compare(T x, T y) 
        {
            foreach (var prop in Properties) 
            {
                //The properties can be any type including null.
                var comp = Comparer.DefaultInvariant.Compare(prop(x), prop(y));   
                if (comp != 0)
                    return comp;
            }
            return 0;
        }
    }
}


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