23种设计模式之单例模式（Singleton）

单例模式确保某一个类只有一个实例，而且自行实例化并向整个系统提供这个实例，这个类称为单例类，它提供全局访问的方法。

public class SingleTon
{
    private static SingleTon singleTon = null;//声明并初始化为null
    public SingleTon()
    {  

    }  

    /// <summary>
    /// 创建SingleTon对象
    /// </summary>
    /// <returns></returns>
    public static SingleTon GetInstance()
    {
        if (singleTon == null)
        {
            singleTon = new SingleTon();
        }
        return singleTon;
    }  

    /// <summary>
    /// 调用测试方法
    /// </summary>
    public void Print()
    {
        Console.WriteLine("打印吧");
    }
}  

class Program
{
    static void Main(string[] args)
    {
        //单例模式
        SingleTon singleTon1 = SingleTon.GetInstance();
        SingleTon singleTon2 = SingleTon.GetInstance();
        SingleTon singleTon3 = SingleTon.GetInstance();
        SingleTon singleTon4 = SingleTon.GetInstance();
        SingleTon singleTon5 = SingleTon.GetInstance();  

        if (singleTon1 == singleTon2 && singleTon2 == singleTon3 && singleTon3 == singleTon4 && singleTon4 == singleTon5)
        {
            Console.WriteLine("相等");
            singleTon1.Print();
        }
    }
}