.Net Interview Questions, Resources, Tips & Tricks.

String objects are immutable as its state cannot be modified once created.
Every time when we perform any operation like copy, replace, case conversion or when we pass a string object as a parameter to a method a new object will be created.

Example:

String s = "ABC";
s.Replace("A","X");

Here Replace() method will not change data that s contains, instead a new string object is created to hold data "XBC" and the reference to this object is returned by Replace() method.

So in order to point s to this object we need to write below line.
s = s.Replace("A","X");