从接口调用“ IsAssignableFrom”不会返回具体的类 [英] Calling 'IsAssignableFrom' from an interface doesn't return the concrete class

问题描述

我试图返回实现下面代码中定义的接口的类的对象类型。

I am trying to return the object type of the class that implements the interface defined in the code below.

linq语句仅返回接口本身，因此控制台输出为：

The linq statement only returns the interface itself, and so the console output is just:

AssignableExperiment.IRule

AssignableExperiment.IRule

为什么不返回具体的类？

Why isn't the concrete class being returned?

using System;
using System.Linq;

namespace AssignableExperiment
{
    public interface IRule
    {
        void Validate(string s);
    }

    public class ConcreteRule : IRule
    {
        public void Validate(string s)
        {
           // some logic
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var ruleType = typeof(IRule);

            var ruleTypes = from t in ruleType.Assembly.GetTypes()
                            where t.IsAssignableFrom(ruleType)
                            select t;

            foreach (var type in ruleTypes)
            {
                Console.WriteLine(type);
            }

            Console.ReadLine();
        }
    }
}

推荐答案

您应该绕过 IsAssignableFrom MSDN 。因为 IsAssignableFrom 可以按照预期的另一种方式工作： BaseType.IsAssignableFrom（DerviedType）返回true。

You should turn it around the IsAssignableFrom MSDN. Because IsAssignableFrom works another way around as expected: BaseType.IsAssignableFrom(DerviedType) returns true.

var ruleTypes = from t in ruleType.Assembly.GetTypes()
                            where ruleType.IsAssignableFrom(t)
                            select t;

如果您不想找回 IRule ：

var ruleTypes = from t in ruleType.Assembly.GetTypes()
                            where ruleType.IsAssignableFrom(t) && t != ruleType
                            select t;

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