单例模式的三种实现方法

第一种、双锁定法 

public sealed class Singleton
    {
static Singleton instance = null;
static readonly object lockhelper = new object();

        Singleton()
        {
        }

public static Singleton Instance
        {
get
            {
if (instance == null)
                {
lock (lockhelper)
                    {
if (instance == null)
                        {
                            instance = new Singleton();
                        }
                    }
                }
return instance;
            }
        }
    }

 

第二种、静态初始化

public sealed class Singleton
    {
static readonly Singleton instance = new Singleton();

static Singleton()
        {
        }

        Singleton()
        {
        }

public static Singleton Instance
        {
get
            {
return instance;
            }
        }
    }

 

第三种、延时初始化

public sealed class Singleton
    {
        Singleton()
        {
        }

public static Singleton Instance
        {
get
            {
return Nested.instance;
            }
        }

class Nested
        {
static Nested()
            {
            }

internal static readonly Singleton instance = new Singleton();
        }
    }