为什么我需要在C#显式实现中将'this'转换为接口类型? [英] Why do I need to cast 'this' to interface type in a C# explicit implementation?

问题描述

我有一个界面:

public interface Profile
{
    string Name { get; }
    string Alias { get; set; }
}

所有实现 Profile 的对象都有一个 Name 和一个 Alias ，但是有些对象会限制 Alias ，这样始终与 Name 相同.施加此限制的用户可以这样实现 Alias :

All objects that implement Profile have a Name and an Alias, but some restrict Alias such that it's always the same as Name. The ones that apply this restriction can implement Alias like this:

string Profile.Alias
{
    get
    {
        return ((Profile)this).Name;
    }
    set { }
}

因为在明确接口实现的上下文中， this 只能是 Profile 类型，我们知道它是通过 Profile 访问的接口而不是包含类的接口或它实现的任何其他接口，为什么需要强制转换?

Since this within the context of an explicit interface implementation can only possibly be of type Profile and we know it was accessed through the Profile interface rather than that of the containing class or any other interface it implements, why is the cast required?

为getter实现使用 return this.Name; 会导致以下错误:

Using return this.Name; for the getter implementation results in this error:

Type `ConcreteProfile' does not contain a definition for `Name' and no extension method `Name' of type `ConcreteProfile' could be found (are you missing a using directive or an assembly reference?)

推荐答案

因为在明确接口实现的上下文中， this 只能为 Profile

这不是事实.您正在 ConcreteProfile 类中实现 Profile.Alias .在这种情况下， this 指的是 ConcreteProfile 实例，可用于访问 ConcreteProfile 实例的任何成员.

This is not true. You are implementing Profile.Alias inside the ConcreteProfile class. In this context, this refers to the ConcreteProfile instance and can be used to access any member of the ConcreteProfile instance.

例如， ConcreteProfile 类可以包含另一个 Name 属性，而不是 Profile.Name .在这种情况下， this.Name 将引用该属性.

For example, the ConcreteProfile class can contain another Name property that is not Profile.Name. In this case this.Name would refer to that property.

由于要访问 Profile.Name ，因此必须将 this 强制转换为 Profile .

Since you want to access Profile.Name, you have to cast this to Profile.

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