如何在C#中使用派生类型重写泛型方法 [英] How to override generic method with derived type in c#

问题描述

我有以下课程:

public interface IService
{
    void ApplyChanges<T>(T parameters) where T : ParamBase;
}

public class ServiceBase : IService
{
    public virtual void ApplyChanges<T>(T parameters) where T : ParamBase
    { }
}
public abstract class Service : ServiceBase
{
    public override void ApplyChanges<T>(T parameters) where T : ParamBase
    {
        Console.WriteLine(parameters.Param2);
        //Apply changes logic here...
    }
}

public abstract class ParamBase
{
    public string Param1 { get; set; }
}

public class ParamA : ParamBase
{
    public string Param2 { get; set; }
}

这是我的考试主要班级:

Here my test main class:

void Main()
{
  var service = new Service();
  var paramA = new ParamA();
  paramA.Param2 = "Test2";
  service.ApplyChanges<ParamA>(paramA);
}

该实现有什么问题?如何从Service类中重写的 ApplyChanges 方法访问 parameters.Param2 ?

What is wrong with that implementation? How can I access parameters.Param2from the overriden ApplyChanges method in my Service class?

总体思路是，我有一个ServiceBase，并且希望其派生类能够将不同的参数类型传递给ApplyChanges方法.

The general idea is that I have a ServiceBase and I want to be able for its derived classes to pass different parameter types to the ApplyChanges method.

推荐答案

我在这里取得了飞跃，但这听起来像您打算拥有多个服务"，每个服务都具有关联的参数类型.

I'm making a leap here, but it sounds like you intend to have multiple "services", each with an associated parameter type.

将类型参数放在方法上，迫使该方法的所有实现都是多态的.(此技术术语为 高级量化 .)

Putting a type parameter on the method, as you have done in the example, forces all implementations of that method to be polymorphic. (The technical term for this is higher-rank quantification.)

相反，您应该将type参数与服务本身相关联.这允许合同的给定实现声明与之关联的参数类型.当您使用它时，我不会理会基类或类型界限.

Instead, you should associate the type parameter with the service itself. This allows a given implementation of the contract to declare which parameter type it's associated with. While you're at it, I wouldn't bother with the base classes or the type bounds.

interface IService<in T>
{
    void ApplyChanges(T param);
}

class Param1
{
    public int X { get; set; }
}
class Service1 : IService<Param1>
{
    public void ApplyChanges(Param1 param)
    {
        param.X = 123;
    }
}

class Param2
{
    public int Y { get; set; }
}
class Service2 : IService<Param2>
{
    public void ApplyChanges(Param2 param)
    {
        param.Y = 456;
    }
}

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