Chapter106:Immutability

Section106.1:System.Stringclass

InC#(and.NET)astringisrepresentedbyclassSystem.String.Thestringkeywordisanaliasforthisclass. The System.String class is immutable, i.e once created its state cannot be altered.

SoalltheoperationsyouperformonastringlikeSubstring,Remove,Replace,concatenationusing+operatoretc will create a new string and return it.

Seethefollowingprogramfordemonstration-

stringstr=”mystring”;

stringnewString=str.Substring(3);

Console.WriteLine(newString);

Console.WriteLine(str);

Thiswillprintstringandmystringrespectively.

Section106.2:Stringsandimmutability

Immutabletypesaretypesthatwhenchangedcreateanewversionoftheobjectinmemory,ratherthanchanging theexistingobjectinmemory.Thesimplestexampleofthisisthebuilt-instringtype.

Takingthefollowingcode,thatappends”world”ontotheword”Hello”

stringmyString=”hello”;

myString+=”world”;

Whatishappeninginmemoryinthiscaseisthatanewobjectiscreatedwhenyouappendtothestringinthe secondline.Ifyoudothisaspartofalargeloop,thereisthepotentialforthistocauseperformanceissuesinyour application.

ThemutableequivalentforastringisaStringBuilder

Takingthefollowingcode

StringBuildermyStringBuilder=newStringBuilder(“hello”);myStringBuild

er.append(“world”);

When you run this, youare modifying the StringBuilderobjectitself in memory.