How is this returning a new instance?

Question

Hi

Given the following code example

// It returns the altered argument as a new instance of string.

public static string BetterThanPassTheReference(string argument)
{ return argument + " ABCDE"; }

I might be missing something obvious here but how is this method returning a new instance of string?

Could this be a shorthand notation for the following:-

String returnArguement = arguement + "ABCDE";

return returnArguement;

Regards

Vulpes · Answer

Strings in .NET are immutable. Once you've created an instance it cannot be changed. So when you concatenate two strings a new instance of string is created which consists of the characters of the first string followed by the characters of the second. Similarly all the methods of the string class which might appear to be altering a string are in fact returning a new instance of it.

Vulpes · Answer

Another class which is immutable is Delegate. Also most of the structs in the .NET framework are immutable : Int32 Char Boolean Double DateTime etc.