What is the difference between string and StringBuilder?

Question

ICSM Computer · Answer

String vs StringBuilder in C#

String	StringBuilder
Immutable (cannot be changed after creation)	Mutable (can be modified)
Every change creates a new string object	Changes occur in the same buffer/object
Slower for repeated concatenation in loops	Faster for frequent append/insert/remove operations
Suitable for fixed or rarely changing text	Suitable for dynamically changing text
Defined in `System.String`	Defined in `System.Text.StringBuilder`

Example:

// String
string str = "Hello";
str += " World";   // Creates a new string object

// StringBuilder
StringBuilder sb = new StringBuilder("Hello");
sb.Append(" World");   // Modifies existing buffer

Interview answer (short):

string is immutable, meaning any modification creates a new object. StringBuilder is mutable, allowing text to be modified without creating new objects repeatedly, making it more efficient for frequent string manipulations.

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What is the difference between string and StringBuilder?

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String vs StringBuilder in C#