A simple question regarding String

[uusheikh]

Hi, i'm confused. If String is a reference type, why b does not change if a is modified, since b is just referring to a? E.g.

String a = "Hello";
String b = a;

a = a.ToUpper();

Console.WriteLine(a);
Console.WriteLine(b);

HELLO
hello

Thanks

[Lost User]

uus831 wrote:

If String is a reference type, why b does not change if a is modified, since b is just referring to a?

You're not passing a reference to a string, but invoking a method on such a reference, and putting the result back in a. The documentation[^] says that this method returns a copy of the string;

' Returns a copy of this String converted to uppercase.

The method ToUpper is executed, and it returns a reference to a new string. This pointer is then stored in your A-variable, not touching B.

I are Troll :suss:

[Lost User]

Because it's not a.ToUpper() but a = a.ToUpper() - ToUpper doesn't change anything, it returns a new string. If you change the actual string (yes you can, unsafe code), b should probably change

[uusheikh]

Ok, i understand. Thanks.

[Ben Fair]

Yes, Microsoft purposely made the String type act like a value type, even though it is really a reference type; it is immutable. Any operations on a String produce a copy, or a partial copy, of the String; the underlying string data cannot be directly changed. This is why you have to do a = a.ToUpper(); in the first place, rather than the ToUpper() method directly changing the String. This is also the reason that the StringBuilder class exists, because it allows string manipulation without the extra copying, and thus has better performance in situations where lots of string manipulation will be happening.