インデクサにデリゲート

gistfile1.cs

using System;
using System.Collections.ObjectModel;
using System.Linq;

namespace インデクサにデリゲート {
	class Program {
		static void Main(string[] args) {
			SampleCollection sample = SampleCollection.My;
			sample.Add(new Hoge() { ID = 1, Name = "A" });
			sample.Add(new Hoge() { ID = 2, Name = "B" });
			sample.Add(new Hoge() { ID = 3, Name = "C" });
			sample.Add(new Hoge() { ID = 4, Name = "D" });
			sample.Add(new Hoge() { ID = 5, Name = "E" });
			sample.Add(new Hoge() { ID = 6, Name = "F" });
			//sample.Add(new Hoge() { ID = 3, Name = "G" }); //エラー

			var r1 = sample[x => x.ID == 2];
			Console.WriteLine("{0}:{1}", r1.ID, r1.Name);	//2:B

			var r2 = sample[x => x.Name == "F"];
			Console.WriteLine("{0}:{1}", r2.ID, r2.Name);	//6:F

			//var r3 = sample[x => x.ID == 100];//エラー

			Console.Read();
		}
	}

	public class SampleCollection : KeyedCollection<int, Hoge> {
		static SampleCollection _this;

		private SampleCollection() {
		}

		~SampleCollection() {
			if (_this != null) {
				_this.Clear();
				_this = null;
			};
		}

		public static SampleCollection My {
			get {
				if (_this == null) _this = new SampleCollection();
				return _this;
			}
		}

		public Hoge this[Func<Hoge, bool> predicate] {
			get { return _this.First(predicate); }
		}

		protected override int GetKeyForItem(Hoge item) {
			return item.ID;
		}
	}

	public class Hoge {
		public int ID { get; set; }
		public string Name { get; set; }
	}
}