为什么不调用重载方法? [英] Why isn't the overloaded method getting called?

问题描述

我认为正在调用的方法是确定的运行时，还是我错过了什么?示例代码:

I thought the method that is getting called is decided runtime, or have I missed something? Sample code:

class Program
{
    static void Main(string[] args)
    {
        var magic = new MagicClass();
        magic.DoStuff(new ImplA());
        magic.DoStuff(new ImplB());
        Console.ReadLine();
    }
}
class MagicClass
{
    internal void DoStuff<T>(T input) where T : SomeBase
    {
        HiThere(input);
    }

    void HiThere(SomeBase input)
    {
        Console.WriteLine("Base impl");
    }

    void HiThere(ImplA input)
    {
        Console.WriteLine("ImplA");
    }

    void HiThere(ImplB input)
    {
        Console.WriteLine("ImplB");
    }
}

abstract class SomeBase
{

}
class ImplA : SomeBase{}
class ImplB : SomeBase{}

我想我会得到:

ImplA
ImplB

作为输出，但会打印 Base impl .在不强制转换输入的情况下，我能做些什么来获取重载方法吗?

as output but it prints Base impl. Is there anything I can do to get the overloaded method without casting the input?

推荐答案

重载由编译器选择.对于此处的通话:

Overloads are chosen by the compiler. For the call here:

internal void DoStuff<T>(T input) where T : SomeBase
{
    HiThere(input);
}

它选择带有 SomeBase 的代码，因为这就是编译时的全部内容.

it chooses the one with SomeBase, because that's all it has at compile time.

您最可能想要的是覆盖.这意味着必须将不同的逻辑放入SomeBase的继承者中:

What you most probably want is overrides. This means that the different logic has to be put into the inheritors of SomeBase:

abstract class SomeBase
{
  abstract string Name { get; }
}
class ImplA : SomeBase{ override string Name { get { return "ImplA"; } } }
class ImplB : SomeBase{ override string Name { get { return "ImplB"; } } }

void HiThere(SomeBase input)
{
    Console.WriteLine(input.Name);
}

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