如何合并泛型类型事件处理程序的附件

Question

我有一个动物接口，我有一些实现接口的类。

public interface IAnimal
{
    int LegCount { get; }
}
public class Dog : IAnimal
{
    public int LegCount { get { return 4; } }
}
public class Octopus : IAnimal
{
    public int LegCount { get { return 8; } }
}

我有一个通用的 EventArgs 类，它有一个指定类型的动物的实例。

public class AnimalRequiredEventArgs<TAnimal> : EventArgs
    where TAnimal : class, IAnimal
{
    public TAnimal Animal { get; set; }
}

我有一个类，其中包含需要指定类型的动物实例的事件。

public class MyClass
{
    public event EventHandler<AnimalRequiredEventArgs<Dog>> DogRequired;
    public event EventHandler<AnimalRequiredEventArgs<Octopus>> OctopusRequired;
}

我有一个类，它有一个事件处理程序，该处理程序将指定类型的动物设置为事件参数的通用属性。

public class AnimalsManager
{
    private readonly IList<IAnimal> _animals =
        new List<IAnimal>{new Dog(), new Octopus()};
    public void OnAnimalRequired<TAnimal>(object sender, AnimalRequiredEventArgs<TAnimal> e)
        where TAnimal : class, IAnimal
    {
        e.Animal = _animals.OfType<TAnimal>().FirstOrDefault();
    }
}

如何合并泛型类型事件处理程序的附件，如下所示？

public class Program
{
    public static void Main()
    {
        var manager = new AnimalsManager();
        var mine = new MyClass();
        // How can I unite these event handler attachments?
        mine.DogRequired += manager.OnAnimalRequired;
        mine.OctopusRequired += manager.OnAnimalRequired;
    }
}

Answer 1

解决此问题的一种方法是创建动物类：

public interface IAnimal
{
    int LegCount { get; }
}
public abstract class Animal: IAnimal
{
     public virtual int LegCount {get{return 4;}}   
     public event EventHandler<AnimalRequiredEventArgs<Animal>> AnimalRequired;
     protected virtual void OnAnimalRequired(AnimalRequiredEventArgs e)
        {
            // Make a temporary copy of the event to avoid possibility of
            // a race condition if the last subscriber unsubscribes
            // immediately after the null check and before the event is raised.
            EventHandler<AnimalRequiredEventArgs<Animal>> handler = AnimalRequired;
            if (handler != null)
            {
                handler(this, e);
            }
        }
}
public class Dog : Animal
{
    public override int LegCount { get { return 4; } }
}
public class Octopus : IAnimal
{
    public override int LegCount { get { return 8; } }
}

然后，如果需要，可以在每个派生类中重写 OnAnimalRequired。

对于客户端，抽象基类将公开单个事件。

希望这有帮助。