Question

Take the following code:

public static string ReverseIt(string myString)
{
    char[] foo = myString.ToCharArray();
    Array.Reverse(foo);
    return new string(foo);
}

I understand that strings are immutable, but what I don’t understand is why a new string needs to be called?

return new string(foo);

Instead of

return foo.ToString();

I have to assume it has something to do with reassembling the CharArray (but that’s just a guess).

What’s the difference between the two and how do you know when to return a new string as opposed to returning a System.String that represents the current object?

Answer 1

Quite simply, because calling ToString() on a char array gives you

System.Char[]

Try

    char[] ca = "Hello world".ToCharArray();
    Console.WriteLine("{0}", ca);

You don’t get Hello World

Also calling Array.Reverse to reverse strings is a bad idea, Tony and Jon mention it in their – now famous – Stack Overflow Presentation