KeyEqualityComparer

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

namespace Core
{
    /// <summary>
    /// Generice impl of <see cref="IEqualityComparer"/>
    /// </summary>
    /// <example>
    /// var treeComparer = new KeyEqualityComparer<TreeDefinition, int?>((t) => t.TreeID);
    /// </example>
    /// <typeparam name="T">The type of object comparing</typeparam>
    /// <typeparam name="TKey">The type of key comparing</typeparam>
    public class KeyEqualityComparer<T, TKey> : IEqualityComparer<T>
    {
        protected readonly Func<T, TKey> keyExtractor;

        public KeyEqualityComparer(Func<T, TKey> keyExtractor)
        {
            this.keyExtractor = keyExtractor;
        }

        public virtual bool Equals(T x, T y)
        {
            return this.keyExtractor(x).Equals(this.keyExtractor(y));
        }

        public int GetHashCode(T obj)
        {
            return this.keyExtractor(obj).GetHashCode();
        }
    }
}