如何动态创建一个动作<T>在运行时? [英] How can I dynamically create an Action<T> at runtime?

问题描述

我希望能够在运行时执行以下等效操作:

I want to be able to do the equivalent to the following at runtime:

var action = new Action<ANYTHING AT RUNTIME>(obj => Console.WriteLine("Called = " + obj));

我知道我需要为 Action 获取正确的类型，但不确定如何使用 Delegate.Create 获取最终位.Type 表示 Action 定义中的 T.

I know I need to get the correct type for the Action, but not sure how to get the final bit using Delegate.Create. Type represent T in the Action definition.

var actionType = typeof(Action<>).MakeGenericType(Type);
var constructor = actionType.GetConstructors()[0];
var @delegate = Delegate.CreateDelegate(actionType, <WHAT GOES HERE>);

人们似乎缺少的一点是我正在尝试创建一个 Action 实例，其中 T 不能静态指定，因为它是从派生自 Attribute 的类中使用的 - 这意味着 T 可以是任何东西，它不能被定义为泛型定义

the point people seem to be missing is I'm trying to create an instance of Action where T can not be specified statically because it is being used from a class derived from Attribute - this means T could be anything and it can not be defines as a generic definition

干杯

推荐答案

如果你知道你需要执行的操作是什么以及如何执行它而不考虑类型(如你的示例)，为什么不只创建一个通用方法执行操作并以这种方式创建您的委托?

If you know what the operation you need to perform is and how to perform it regardless of type (as in your example) why not just make a generic method that performs the operation and create your delegate that way?

class Program
{
    public static void Perform<T>(T value)
    {
        Console.WriteLine("Called = " + value);
    }

    public static Delegate CreateAction(Type type)
    {
        var methodInfo = typeof (Program).GetMethod("Perform").MakeGenericMethod(type);
        var actionT = typeof (Action<>).MakeGenericType(type);
        return Delegate.CreateDelegate(actionT, methodInfo);
    }

    static void Main(string[] args)
    {
        CreateAction(typeof (int)).DynamicInvoke(5);
        Console.ReadLine();
    }
}

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