Question

i am reading Accelerated C# 2010. and have a few questions

Question 1

Instances of String are immutable in
the sense that once you create them,
you cannot change them

how is that true. i have not used C# for sometime, plus i am just starting so i maybe wrong even in the syntax.

string str1 = "this is a string"; // i hope my syntax is right 
str1 = "this is a NEW string"; // i think i can do this right? 

Question 2

If you call the ICloneable.Clone
method on a string, you get an
instance that points to the same
string data as the source. In fact,
ICloneable.Clone simply returns a
reference to this

if this is true, it means that

string str1 = "string 1";
// i hope my syntax is right too. i am really not sure about this
string str2 = str1.Clone(); 
str2 = "modified string"; // will str1 be modified too? 

Answer 1

string str1 = "this is a string"; // i hope my syntax is right 
str1 = "this is a NEW string"; // i think i can do this right? 

Sure! string is a reference type (a pointer, if you want so see it like this), so in line 2, you are making variable str1 point to a different (constant) string in memory. The original string is not changed, it’s just not referenced any more.

string str1 = "string 1";
string str2 = str1.Clone(); // i hope my syntax is right too. i am really not sure about this
str2 = "modified string"; // will str1 be modified too? 

No, because you didn’t modify "string 1". After line 2, it looked like this:

memory            "string 1"
                    ^    ^ 
                    |    |
stack             str1  str2

After line 3, it looks like this:

memory            "string 1"     "modified string"
                      ^              ^
                      |              |
stack                str1           str2