using System;

using System.Threading;

using System.Threading.Tasks;

namespace SingletonPattern3

{

public class PeriodParser

{

private static PeriodParser instance = new PeriodParser();

private PeriodParser()

{

}

public static PeriodParser GetInstance()

{

return instance;

}

}

public sealed class COMManager

{

private static COMManager instance;

public string Value { get; private set; }

private readonly static object _lock = new object();

private COMManager(string value)

{

this.Value = value;

}

public static COMManager GetInstance(string value)

{

if (instance == null)

{

lock (_lock)

{

if (instance == null)

instance = new COMManager(value);

}

}

return instance;

}

}

// Потокобезопасная реализация без использования lock

public class Singleton2

{

private static readonly Singleton2 instance = new Singleton2();

public string Date { get; private set; }

private Singleton2()

{

Date = System.DateTime.Now.TimeOfDay.ToString();

}

public static Singleton2 GetInstance()

{

return instance;

}

}

// Nested class

public class Singleton

{

public string Date { get; private set; }

public static string text = "hello";

private Singleton()

{

Console.WriteLine($"Singleton ctor {DateTime.Now.TimeOfDay}");

Date = DateTime.Now.TimeOfDay.ToString();

}

public static Singleton GetInstance()

{

Console.WriteLine($"GetInstance {DateTime.Now.TimeOfDay}");

Thread.Sleep(500);

return Nested.instance;

}

private class Nested

{

static Nested() { }

internal static readonly Singleton instance = new Singleton();

}

}

class Program

{

static void Main(string[] args)

{

var t1 = Task.Run(() =>

{

Thread.Sleep(300);

COMManager manager = COMManager.GetInstance("Foo");

Console.WriteLine(manager.Value);

});

var t2 = Task.Run(() =>

{

COMManager manager = COMManager.GetInstance("Barr");

Console.WriteLine(manager.Value);

});

Task.WaitAll(t1, t2);

}

}

}