c＃编译器会执行多个隐式转换以从一种类型到另一种类型吗？ [英] Will the c# compiler perform multiple implicit conversions to get from one type to another?

问题描述

我们假设你有一个类如下：

Let's say you have yourself a class like the following:

public sealed class StringToInt { 
    private string _myString; 
    private StringToInt(string value) 
    { 
        _myString = value; 
    } public static implicit operator int(StringToInt obj) 
    { 
        return Convert.ToInt32(obj._myString); 
    } 
    public static implicit operator string(StringToInt obj) 
    { 
        return obj._myString; 
    } 
    public static implicit operator StringToInt(string obj) 
    { 
        return new StringToInt(obj); 
    } 
    public static implicit operator StringToInt(int obj) 
    { 
        return new StringToInt(obj.ToString()); 
    } 
}

然后，您将能够编写如下代码：

Will you then be able to write code like the following:

MyClass.SomeMethodThatOnlyTakesAnInt(aString);

没有说明没有从字符串到int的隐式转换？

without it stating that there is no implicit cast from string to int?

[是的，我可以自己测试，但我想我会把它放在那里，看看所有的大师必须说什么]

[Yes, i could test it myself but i thought i would put it out there and see what all of the gurus have to say]

推荐答案

我相当肯定这是不可能的C＃3.0。 参考中涵盖转化的部分为6.4。也就是说，6.4.4用户定义的隐式转换。

I am fairly certain this is not possible under C# 3.0. The sections in the reference that covers conversions is 6.4. Namely, 6.4.4 "User-defined implicit conversions".

它只谈到从S-> T（而不是S-> T-> U）涵盖以下情况：

It only talks about conversions from S->T (and not S->T->U) which covers the cases such as:

StringToInt _t = "foo";
int t = _t;

和

int t = (StringToInt)"foo";

这两种情况都只涉及S-> T（两次）。

Where both of these cases only involve S->T (twice).

我确定这不可能在C＃3.0。
允许S-> T-> U至少需要遵循指定的算法，才需要类型匹配器执行更多的工作。

I am pretty sure this is not possible in C# 3.0. Allowing S->T->U would require much more work to be performed by the type matcher, at least following the algorithm specified.

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