动态动作< T> ：执行时无效的参数 [英] Dynamic Action<T> : Invalid Arguments when executed

问题描述

我在我正式的大小的项目中有很多地方，我需要打开一个类型。显然，我不能在.NET中做到这一点（以一种简单的方式来满足我的需求），所以我必须做一个体面的投射。这个代码是试图隐藏一些概念证明的结果。

我有一个简单的继承模型：

  public class Base {} 
 public class Derived：Base {public string Name {get;组; 
  

和我的课程：

  public sealed class TypeSwitch< T> 
 {
私人字典<类型，动态> _dict; 
 
 public TypeSwitch（）
 {
 _dict = new Dictionary< Type，dynamic>（）; 
} 
 
 public TypeSwitch< T>在其中K：T 
 {
 _dict.Add（typeof（K），action））中添加< K>（Action< K> 
返回这个; 
} 
 
 public void Execute（T item）
 {
 var type = item.GetType（）; 
 var action = _dict [type]; 
 
 action（item）; 
} 
} 
  

我运行它：

  static void Main（string [] args）
 {
 var ts = new TypeSwitch< Base>（）; 
 ts.Add< Derived>（d => {Console.WriteLine（d.Name）;}）; 
 
 Base b = new Derived {Name =Jonesopolis}; 
 ts.Execute（b）; 
} 
  

当我到达 action（item）我得到一个 RuntimeBinderException 说

附加信息： System.Action< ConsoleApp.Derived>'有一些无效的参数

如果我可以使它工作，这将是非常光滑和有用的。有人向我解释我失踪了吗？有可能得到这个工作吗？

解决方案

尝试另一个级别的lambdas。除了工作，我预计这将比使用动态更快，即使有两个代理被调用。

  public sealed class TypeSwitch< T> 
 {
私人字典< Type，Action< T>> _dict; //不再动态
 
 public TypeSwitch（）
 {
 _dict = new Dictionary< Type，Action< T>（）; //不再动态
} 
 
 public TypeSwitch< T>其中K：T 
 {
 _dict.Add（typeof（K），o => action（（K）o））;< K>（Action< K> //外lambda在调用内部lambda之前转换该值
返回此值; 
} 
 
 public void Execute（T item）
 {
 var type = item.GetType（）; 
 var action = _dict [type]; 
 action（item）; 
} 
} 
  

I have a lot of places in my decently sized project where I need to switch on a type. Obviously I can't do that in .NET (in a way simple enough to satisfy me), so I have to do a decent amount of casting. This code is the result of trying to hide some of that in a proof of concept.

I have a simple inheritence modeled:

public class Base { }
public class Derived : Base { public string Name { get; set; } }

and my class:

public sealed class TypeSwitch<T> 
{
    private Dictionary<Type, dynamic> _dict;

    public TypeSwitch()
    {
        _dict = new Dictionary<Type, dynamic>();
    }

    public TypeSwitch<T> Add<K>(Action<K> action) where K : T
    {
        _dict.Add(typeof(K), action);
        return this;
    } 

    public void Execute(T item)
    {
        var type = item.GetType();
        var action = _dict[type];

        action(item);
    }
}

and I run it with:

static void Main(string[] args)
{
    var ts = new TypeSwitch<Base>();
    ts.Add<Derived>(d => { Console.WriteLine(d.Name); });

    Base b = new Derived { Name = "Jonesopolis" };
    ts.Execute(b);
}    

When I get to action(item) I get a RuntimeBinderException saying

Additional information: Delegate 'System.Action<ConsoleApp.Derived>' has some invalid arguments

This would be pretty slick and helpful if I could get it working. Can someone explain to me what I'm missing? Is it possible to get this working?

解决方案

Try another level of lambdas. In addition to working, I expect this would be considerably faster than using dynamic, even though there are two delegates being invoked.

public sealed class TypeSwitch<T>
{
    private Dictionary<Type, Action<T>> _dict; // no longer dynamic

    public TypeSwitch()
    {
        _dict = new Dictionary<Type, Action<T>>();  // no longer dynamic
    }

    public TypeSwitch<T> Add<K>(Action<K> action) where K : T
    {
        _dict.Add(typeof (K), o => action((K) o)); // outer lambda casts the value before calling the inner lambda
        return this;
    }

    public void Execute(T item)
    {
        var type = item.GetType();
        var action = _dict[type];
        action(item);
    }
}

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