C# - Difference between String and Stringbuilder in C#, Asp.net

String

String is immutable. Immutable means once we create string object we cannot modify. Any operation like insert, replace or append happened to change string simply it will discard the old value and it will create new instance in memory to hold the new value.

Example

string str = "hi"; // create a new string instance instead of changing the old one str += "test"; str += "help";

String Builder

String builder is mutable it means once we create string builder object we can perform any operation like insert, replace or append without creating new instance for every time.

Example

StringBuilder sb = new StringBuilder(""); sb.Append("hi"); sb.Append("test "); string str = sb.ToString();

Differences

String	StringBuilder
It’s an immutable	It’s mutable
Performance wise string is slow because every time it will create new instance	Performance wise stringbuilder is high because it will use same instance of object to perform any action
In string we don’t have append keyword	In StringBuilder we can use append keyword
String belongs to System namespace	Stringbuilder belongs to System.Text namespace