IEnumerable<int> Numbers()
{
    Console.WriteLine("Start");
    yield return 1;
    Console.WriteLine("Middle");
    yield return 2;
    Console.WriteLine("End");
}

foreach (var num in Numbers().Take(1))
{
    Console.WriteLine(num);
}

var numbers = new List<int> { 1, 2, 3 };
var query = numbers.Where(n => n > 1);

numbers.Add(4);

foreach (var n in query)
    Console.Write(n + " ");

Архитектура компьютерных систем. Как собрать современный компьютер по всем правилам

using System;

class Program
{
    static int Test()
    {
        try
        {
            return 1;
        }
        finally
        {
            Console.WriteLine("finally");
        }
    }

    static void Main()
    {
        Console.WriteLine(Test());
    }
}

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var actions = new List<Action>();

        for (int i = 0; i < 3; i++)
        {
            actions.Add(() => Console.Write(i));
        }

        foreach (var action in actions)
        {
            action();
        }
    }
}

using System;

class Program
{
    static void Main()
    {
        string a = "hello";
        string b = "he" + "llo";

        Console.WriteLine(object.ReferenceEquals(a, b));
    }
}