Question

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()); 
    } 
}

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

MyClass.SomeMethodThatOnlyTakesAnInt(aString);

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

[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]

Answer 1

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”.

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;

and

int t = (StringToInt)"foo";

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

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.