c#为什么delegate\event在传递给另一个类后没有得到更新

Question

我在调用将事件传递给特定类后添加的委托时遇到问题，我认为委托将更新作为对象..

例如，我将委托传递给的类：

更新代码（由于 cmets 中的一些问题）

这实际上是 +- 我需要如何运行它，“ExecutorOnCalculationCompleted”从不调用（请忽略睡眠和同步，我将代码缩小到所需部分）

    class Executor
{

    public delegate void CalculationCompletEventHandler(int score);

    public event CalculationCompletEventHandler CalculationCompleted;

    public void Start()
    {
        CalculationCompleted += OnCalculationCompleted;
        Plus plus = new Plus(1, 2, CalculationCompleted);
        Minus minus =  new Minus(5, 2, CalculationCompleted);
        Multi multi =  new Multi(5, 2, CalculationCompleted);
        ...
        ...    They will work async...
    }

    private void OnCalculationCompleted(int score)
    {
        Console.WriteLine("OnCalculationCompleted , score=" + score);
    }
}

class Plus
{
    private Executor.CalculationCompletEventHandler _calculationCompletEventHandler;
    private int a;
    private int b;

    public Plus(int a, int b,Executor.CalculationCompletEventHandler calculationCompletEventHandler)
    {
        this.a = a;
        this.b = b;
        _calculationCompletEventHandler = calculationCompletEventHandler;
    }

    public void Calculate()
    {
        _calculationCompletEventHandler?.Invoke(a+b);
    }
}



class Program
{

    static void Main(string[] args)
    {
        Executor executor = new Executor();
        executor.Start(); // async action
        executor.CalculationCompleted += ExecutorOnCalculationCompleted;
        ...
    }

    // This method doesn't get invoked when the class inside Executor fire the event.
    private static void ExecutorOnCalculationCompleted(int score)
    {
        Console.WriteLine("ExecutorOnCalculationCompleted , score=" + score);
    }
}

Answer 1

您在构造函数中直接传递委托。我想你想把这个事件放到课堂上。示例：

class Plus
{
    public delegate void CalculationCompletEventHandler(int score);
    public event CalculationCompletEventHandler CalculationCompleted;

    private int a;
    private int b;

    public Plus(int a, int b)
    {
        this.a = a;
        this.b = b;
    }

    public void Calculate()
    {
        if (CalculationCompleted != null)
        {
            CalculationCompleted(a + b);
        }
    }
}

你现在可以这样使用它了：

void Main()
{
    Plus plus = new Plus(1, 2);
    plus.CalculationCompleted += OnCalculationCompleted;
    plus.Calculate();

    plus.CalculationCompleted += OnCalculationCompleted2;
    plus.Calculate();        
}

private void OnCalculationCompleted(int score)
{
    Console.WriteLine("OnCalculationCompleted , score=" + score);
}

private void OnCalculationCompleted2(int score)
{
    Console.WriteLine("OnCalculationCompleted2 , score=" + score);
}

正如评论中提到的，如果在程序的不同部分使用委托类型，您可能只需要事件本身。

问题更新后

如果您希望在执行程序中执行该事件，我只需将一个操作传递给您的每个类，例如 Plus、Multiply... 并从执行程序调用该事件：

class Executor
{
    public delegate void CalculationCompletEventHandler(int score);
    public event CalculationCompletEventHandler CalculationCompleted;

    public void Start()
    {
        CalculationCompleted += OnCalculationCompleted;
        Plus plus = new Plus(1, 2, FireEvent);        
    }

    private void FireEvent(int score)
    {
        if (CalculationCompleted != null)
        {
            CalculationCompleted(score);
        }
    }

    private void OnCalculationCompleted(int score)
    {
        Console.WriteLine("OnCalculationCompleted , score=" + score);
    }
}

class Plus
{
    private int a;
    private int b;
    private Action<int> completionAction

    public Plus(int a, int b, Action<int> completionAction)
    {
        this.a = a;
        this.b = b;
        this.completionAction = completionAction;       
    }

    public void Calculate()
    {
        this.completionAction(a + b);
    }
}