Why does `String.Trim()` not trim the object itself?

Question

Not often but sometimes I need to use String.Trim() to remove whitespaces of a string.
If it was a longer time since last trim coding I write:

string s = " text ";
s.Trim();

and be surprised why s is not changed. I need to write:

string s = " text ";
s = s.Trim();

Why are some string methods designed in this (not very intuitive) way? Is there something special with strings?

Answer 1

Strings are immutable. Any string operation generates a new string without changing the original string.

From MSDN:

Strings are immutable--the contents of a string object cannot be changed after the object is created, although the syntax makes it appear as if you can do this.