C#:通用方法不调用特定方法重载

C#: Generic method doesn#39;t call specific method overload(C#:通用方法不调用特定方法重载)

问题描述

我正在尝试在 C# 中创建一个泛型方法，它将根据其主体中的参数数据类型调用不同的方法，然后处理它们的结果.我试图通过创建一个通用包装器方法来实现这一点，然后提供处理方法的几个重载 - 包括一个通用的，如果没有特定的重载可用.

I am trying to create a generic method in C#, which will call different methods based on the argument datatype in its body and process their result afterwards. I am trying to achieve this by creating a generic wrapper method and then provide several overloads of the processing method - including a generic one that'll be used if no specific overload is available.

当我直接调用处理方法时，正确选择了适当的版本.但是，当我从包装器方法调用它时，它总是选择通用的，即使我传递给它的特定数据类型存在匹配的重载.

When I call the processing method directly, appropriate version is correctly selected. However when I call it from the wrapper method it always selects the generic one, even if there's a matching overload for the specific datatype I passed to it.

有什么方法可以调整代码以使其按我需要的方式运行?还是我必须使用不同的方法.

Is there any way to adjust the code to make it behave the way I need to? Or do I have to use a different approach.

我需要代码与 Mono 2.6 兼容.

I need the code to be compatible with Mono 2.6.

using System;

class Program
{
    static void Func<T>(T val)
    {
        Console.WriteLine("Generic Func");
    }

    static void Func(int val)
    {
        Console.WriteLine("Int Func");
    }

    static void Func(string val)
    {
        Console.WriteLine("String Func");
    }

    static void FuncWrap<T>(T val)
    {
        Console.Write("Wrap: ");
        Func(val);
    }

    static void Main(string[] args)
    {
        Func(2);
        Func("Potato");
        Func(2.0);

        FuncWrap(2);
        FuncWrap("Potato");
        FuncWrap(2.0);

        Console.Read();
    }
}

推荐答案

有什么方法可以纠正这种行为吗?

Is there any way correct this behavior?

根据 C# 语言规范，这已经是正确的行为.FuncWrap 中调用的 Func 的重载通常在编译时确定，因此它不能选择不同的 Func 基于执行时类型的重载.

It's already the correct behaviour according to the C# language specification. The overload of Func called within FuncWrap is normally determined at compile time, so it can't pick a different Func overload based on the execution-time type.

然而，改变行为的一种方法是使用动态类型:

One way of changing the behaviour, however, is to use dynamic typing:

static void FuncWrap<T>(T val)
{
    Console.Write("Wrap: ");
    dynamic x = val;
    Func(x);
}

现在将根据 x 值的 实际 类型在执行时执行重载决议.这会产生性能成本，但应该按照您的意愿去做.

That will now perform overload resolution at execution time based on the actual type of the value of x. This incurs a performance cost, but should do what you want it to.

或者，您可以对重载的知识进行硬编码:

Alternatively, you could hard-code knowledge of the overloads:

static void FuncWrap<T>(T val)
{
    Console.Write("Wrap: ");
    if (typeof(T) == typeof(string))
    {
        Func((string)(object)val);
    }
    else if (typeof(T) == typeof(int))
    {
        Func((int)(object)val);
    }
    else
    {
        Func(val);
    }
}

这显然很可怕.

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