C# Operator Overloading, rewriting string?

Question

I'm very fresh to C# Currently learning Operator overloading i'm trying to do something like this:

string val = 500; (I can't implicitly)

and then

Number n1 = val;

I manages to get the Number n1 = someintvalue, for instance:

Number n1 = 500;

like this:

public struct Number
{
    public int Value { get; set; }
    public Number(int Val)
    {
        Value = Val;
    }
    public static implicit operator Number(int num)
    {
        return new Number(num);
    }
}

However, when trying to make Number n1 = val; (when val is a string) I simply cant since the first line cant compile:

string val = 500;

and the following wont work:

public static implicit operator string(int A)
{
    return new string(A);
}

because of 1 error which i can not understand
1)User-defined conversion must convert to or from the enclosing type

by the way i get the idea of op overload
underthis specific case of: return new Number(num); I simply init the ctor
still need some more fundemental understanding thx ahead!

Side note: do not use struct unless you understand the difference between it and class, and explicitly need a struct. Mutable structs can cause all sorts of problems that are usually unnecessary. — D Stanley
– D Stanley, Commented Mar 28, 2016 at 14:40
Plus, string val = 500; is poor practice. If you want a string then use a string: string val = "500"; C# is a strongly-typed language and should be treated as such - adding multiple type conversion overloads erodes that type safety. — D Stanley
– D Stanley, Commented Mar 28, 2016 at 14:42

D Stanley · Accepted Answer · 2016-03-28 14:35:22Z

5

I presume the function you quote is within the Number class. You have added a conversion operator from an int to a string within that class, which is not legal. You can only add operators that convert to or from the type they're defined in, such as:

public static implicit operator string(Number A)
{
    return new string(A.Value);
}

which will fail because string does not have a constructor that takes an int. You could do:

public static implicit operator string(Number A)
{
    return A.ToString();
}

But the standard way to "convert" to a string is to overload the ToString method, which the compiler often calls automatically when a conversion to string is requested:

public override string ToString()
{
    return Value.ToString();
}

edited Mar 28, 2016 at 14:35

answered Mar 28, 2016 at 14:26

D Stanley

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2 Comments

N3wbie Over a year ago

I get what you did here. However, I do not understand how to make the string val = 500; within the void Main

D Stanley Over a year ago

500 is an integer, not a string. There is no implicit conversion from int to string, so you need either string val = "500"; or string val = 500.ToString();. C# is a type-safe language. Don't try to use it like JavaScript.

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