Singleton 单例模式简介与 C# 示例【创建型】【设计模式来了】

public class Singleton
{
    private static Singleton instance = null;
    private static object lockObject = new object();
    /// <summary>
    /// 私有化构造函数，防止外部实例化
    /// </summary>
    private Singleton() { }
    public static Singleton Instance
    {
        get
        {
            if (instance == null)
            {
                lock (lockObject) // 线程同步锁
                {
                    if (instance == null) // Lazy Initialization
                    {
                        instance = new Singleton();
                    }
                }
            }
            return instance;
        }
    }
    /// <summary>
    /// 重置 Singleton
    /// </summary>
    public void Reset()
    {
        instance = null;
    }
}

static void Main(string[] args)
{
    var instance1 = Singleton.Instance;
    var instance2 = Singleton.Instance;
    Console.WriteLine(instance1 == instance2); // 输出 true 
}

public class SingletonParameters
{
    private static SingletonParameters instance = null;
    private static object lockObject = new object();
    private int _firstvalue, _secondvalue;
    /// <summary>
    /// 私有化构造函数，防止外部实例化
    /// </summary>
    private SingletonParameters(int first, int second)
    {
        this._firstvalue = first;
        this._secondvalue = second;
    }
    public static SingletonParameters InstanceParameters(int first, int second)
    {
        if (instance == null)
        {
            lock (lockObject) // 线程同步锁
            {
                if (instance == null) // Lazy Initialization
                {
                    instance = new SingletonParameters(first, second);
                }
            }
        }
        else
        {
            instance.FirstValue = first;
            instance.SecondValue = second;
        }
        return instance;
    }
    public int FirstValue { get { return _firstvalue; } set { _firstvalue = value; } }
    public int SecondValue { get { return _secondvalue; } set { _secondvalue = value; } }
    /// <summary>
    /// 重置 Singleton
    /// </summary>
    public void Reset()
    {
        instance = null;
    }
}

var instance1 = SingletonParameters.InstanceParameters(1, 2);
Console.WriteLine($"FirstValue:{instance1.FirstValue}");
Console.WriteLine($"SecondValue:{instance1.SecondValue}");
var instance2 = SingletonParameters.InstanceParameters(3, 4);
Console.WriteLine($"FirstValue:{instance2.FirstValue}");
Console.WriteLine($"SecondValue:{instance2.SecondValue}");
Console.WriteLine($"instance1 == instance2 : {instance1 == instance2}");