Why is String.Format static? [closed]

Answer 1

I think it's because it's a creator method (not sure if there's a better name). All it does is take what you give it and return a single string object. It doesn't operate on an existing object. If it was non-static, you would need a string to begin with.

Answer 2

@Jared:

Non-overloaded, non-inherited static methods (like Class.b(a,c)) that take an instance as the first variable are semantically equivalent to a method call (like a.b(c))

No, they aren't.

(Assuming it compiles to the same CIL, which it should.)

That's your mistake. The CIL produced is different. The distinction is that member methods can't be invoked on null values so the CIL inserts a check against null values. This obviously isn't done in the static variant.

However, String.Format does not allow null values so the developers had to insert a check manually. From this point of view, the member method variant would be technically superior.

Answer 3

I haven't tried it yet but you could make an extension method for what you want. I wouldn't do it, but I think it would work.

Also I find String.Format() more in line with other patterned static methods like Int32.Parse(), long.TryParse(), etc.

You cloud also just use a StringBuilder if you want a non static format. StringBuilder.AppendFormat()

Answer 4

I think it looks better in general to use String.Format, but I could see a point in wanting to have a non-static function for when you already have a string stored in a variable that you want to "format".

As an aside, all functions of the string class don't act on the string, but return a new string object, because strings are immutable.

Answer 5

Another reason for String.Format is the similarity to function printf from C. It was supposed to let C developers have an easier time switching languages.

Answer 6

I don't know why they did it, but it doesn't really matter anymore:

public static class StringExtension
{
    public static string FormatWith(this string format, params object[] args)
    {
        return String.Format(format, args);
    }
}

public class SomeClass
{
    public string SomeMethod(string name)
    {
        return "Hello, {0}".FormatWith(name);
    }
}

That flows a lot easier, IMHO.