C# StringBuilder

StringBuilder is a Dynamic Object. It doesn’t create a new object in the memory but dynamically expands the needed memory to accommodate the modified or new string.A String object is immutable, i.e. a String cannot be changed once created. To avoid string replacing, appending, removing or inserting new strings in the initial string C# introduce StringBuilder concept.

Declaration and Initialization of StringBuilder

StringBuilder can be declared and initialized the same way as class,

StringBuilder s = new StringBuilder();
            
or

StringBuilder s = new StringBuilder("GeeksforGeeks");

“s” is the object of StringBuilder class. Also, we can pass a string value(here “GeeksforGeeks”) as an argument to the constructor of StringBuilder.

Defining the capacity of StringBuilder

Although the StringBuilder is a dynamic object that allows you to expand the number of characters in the string that it encapsulates, you can specify a value for the maximum number of characters that it can hold. This value is called the capacity of the StringBuilder object.

StringBuilder s = new StringBuilder(20);

or

StringBuilder s = new StringBuilder("GeeksForGeeks", 20);

Here,

• In the 1st statement we pass an integer value as an argument to the constructor. This is the maximum capacity of character that can hold a string.
• In the 2nd statement we pass string value with an integer value (that is the maximum capacity of character a string can hold) as an argument to the constructor.

Important Methods of StringBuilder Class

Example 1: For appending string value in StringBuilder

// Adding element in StringBuilder Object
using System; 
using System.Text; 

class Geeks 
{ 
	// Main Method
	public static void Main() 
	{ 
		// "20" is capacity 
		StringBuilder s = new StringBuilder("HELLO ", 20); 
		
		s.Append("GFG"); 

		// after printing "GEEKS" 
		// a new line append 
		s.AppendLine("GEEKS"); 
		
		s.Append("GeeksForGeeks"); 
		Console.WriteLine(s); 
	} 
} 

HELLO GFGGEEKS
GeeksForGeeks

Example 2: Format the input string into the specified format and then append it.

// Adding the Formatted String in
// StringBuilder Object
using System; 
using System.Text; 

class Geeks 
{ 
	// Main Method 
	public static void Main() 
	{ 
		StringBuilder s = new StringBuilder("Your total amount is "); 

		// using the method 
		s.AppendFormat("{0:C} ", 50); 

		Console.WriteLine(s); 
	} 
} 

Your total amount is ?50.00 

Example 3: Insert string at specified value in StringBuilder object

// Inserting String at specified index
// position/index in StringBuilder 
using System; 
using System.Text; 

class Geeks 
{ 
	// Main Method 
	public static void Main() 
	{ 
		// "20" is capacity 
		StringBuilder s = new StringBuilder("HELLO ", 20); 
		
		// "GEEKS" insert after 6th index 
		s.Insert(6, "GEEKS"); 
		
		Console.WriteLine(s); 
	} 
} 

HELLO GEEKS

Example 4: Removes the specified number of characters from the StringBuilder Object

// Removing elements from particular
// indexes in StringBuilder Object
using System; 
using System.Text; 

class Geeks
{ 
	// Main Method 
	public static void Main() 
	{ 
		// "20" is capacity 
		StringBuilder s = new StringBuilder("GeeksForGeeks", 20); 

		// remove starts from index 5 
		// and remove happes 3 index 
		// after index 5 
		s.Remove(5, 3); 
		
		Console.WriteLine(s); 
	} 
} 

GeeksGeeks

Example 5: Replace characters within the StringBuilder Object

// Replace Elements in StringBuilder Object
using System; 
using System.Text; 

class Geeks
{ 
	// Main Method 
	public static void Main() 
	{ 

		// "20" is capacity 
		StringBuilder s = new StringBuilder("GFG Geeks ", 20); 
		
		// Replace "GFG" with "Geeks For" 
		s.Replace("GFG", "Geeks For"); 

		Console.WriteLine(s); 
	} 
} 

Geeks For Geeks