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CSharp · Console

/Program.cs

using System;
using System.Collections.Generic;
					
public class Program
{
	public static void Main()
	{
		var theOne = FindTheOne();
		Console.WriteLine("The result: {0}", (theOne?.ThisIsTheOne())?.ToString() ?? "nothing");
	}

	private static Value FindTheOne()
	{
		foreach(var i in Values())
		{
			if (i.ThisIsTheOne())
			{
				Console.WriteLine("I found it!");
				return i;
			}
			Console.WriteLine("Not this one");
		}
		Console.WriteLine("Sorry, not found");
		return null;
	}

	private static IEnumerable<Value> Values()
	{
		var badValue = new Value(false);
		var goodValue = new Value(true);
		try {
			yield return badValue;
			yield return goodValue;
		} finally {
			goodValue.Die();
		}
	}

	private class Value
	{
		private bool flag;

		public Value(bool flag)
		{
			this.flag = flag;
		}
		
		public bool ThisIsTheOne() => flag;

		public void Die()
		{
			this.flag = false;
		}
	}
}