using System;

public class Program

{

    public static void Main()

    {

        WeakReference weakRef;

        {

            var obj = new object();

            weakRef = new WeakReference(obj);

            Console.WriteLine(weakRef.IsAlive);

            obj = null;

        }

        GC.Collect();

        GC.WaitForPendingFinalizers();

        Console.WriteLine(weakRef.IsAlive);

    }

}