单例模式
============1单例模式==============
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
namespace ConsoleApplication13
{
class Program
{
static void Main(string[] args)
{
for (int i = 0; i < 1000; i++)
{
Thread t = new Thread(new ThreadStart(() =>
{
Singleton s = Singleton.GetInstance();
}));
t.Start();
}
Console.WriteLine("ok");
Console.ReadKey();
}
}
public class Singleton
{
private Singleton()
{
//只要输出一次.就证明创建了一个对象。
Console.WriteLine(" . ");
}
private static Singleton _instance;
private static readonly object _syn = new object();
public static Singleton GetInstance()
{
//每次都锁定降低性能，所以只有为空值时才锁定。
if (_instance == null)
{
lock (_syn)
{
//为了防止在第一次判断_instance==null后，在锁定之前_instance又被赋值，所以锁定之后一定要再判断一次是否已经创建了对象。
if (_instance == null)
{
_instance = new Singleton();
}
}
}
return _instance;
}
}
}
=============================2单例模式（另一种写法）==========================
public sealed class Singleton2
{
private Singleton2()
{
Console.WriteLine(".");
}
//静态成员初始化，只在第一次使用的时候初始化一次。
private static readonly Singleton2 _instance = new Singleton2();
public static Singleton2 GetInstance()
{
return _instance;
}
}
=================测试====================
for (int i = 0; i < 1000; i++)
{
Thread t = new Thread(new ThreadStart(() =>
{
Singleton2 s = Singleton2.GetInstance();
}));
t.Start();
}
Console.WriteLine("ok");
Console.ReadKey();
//======================实现窗口类(Form)的单例模式===============
public partial class Form2 : Form
{
private Form2()
{
InitializeComponent();
}
private static Form2 f2;
private static readonly object syn = new object();
public static Form2 GetForm2()
{
if (f2 == null || f2.IsDisposed)
{
lock (syn)
{
if (f2 == null || f2.IsDisposed)
{
f2 = new Form2();
}
}
}
return f2;
}
}
