C# Strings

Last Updated : 11 Jan, 2025

In C#, string is a sequence of Unicode characters or array of characters. The range of Unicode characters will be U+0000 to U+FFFF. The array of characters is also termed as the text. So the string is the representation of the text. A string is an important concept and sometimes people get confused whether the string is a keyword or an object or a class. So let’s clear out this concept.

A string is represented by class System.String. The “string” keyword is an alias for System.String class and instead of writing System.String one can use String which is a shorthand for System.String class. So we can say string and String both can be used as an alias of System.String class. So string is an object of System.String class.

Example:

// creating the string using string keyword
string s1 = “GeeksforGeeks”;

// creating the string using String class
String s2 = “GFG”;

// creating the string using String class
System.String s3 = “Pro Geek”;

The String class is defined in the .NET base class library. In other words a String object is a sequential collection of System.Char objects which represents a string. The maximum size of String object in memory is 2GB or about 1 billion characters. System.String class is immutable, i.e once created its state cannot be altered.

// C# program to declare string using
// string, String and System.String
// and initialization of string
using System;

class Geeks 
{
    // Main Method
    static void Main(string[] args)
    {
        // declare a string Name using 
        // "System.String" class
        System.String Name;
        
        // initialization of String
        Name = "Geek";

        // declare a string id using 
        // using an alias(shorthand) 
        // "String" of System.String
        // class
        String id;
        
        // initialization of String
        id = "33";

        // declare a string mrk using 
        // string keyword
        string mrk;
        
        // initialization of String
        mrk = "97";
        
        // Declaration and initialization of
        // the string in a single line
        string rank = "1";

        // Displaying Result
        Console.WriteLine("Name: {0}", Name);
        Console.WriteLine("Id: {0}", id);
        Console.WriteLine("Marks: {0}", mrk);
        Console.WriteLine("Rank: {0}", rank);
    }
}

Output

Name: Geek
Id: 33
Marks: 97
Rank: 1

Key Characteristics of Strings

Immutable: Once created, the content of a string cannot be altered. Any modification results in the creation of a new string.
Reference Type: Strings are reference types, but they behave like value types in some scenarios, such as comparison.
Unicode Support: Strings can contain any Unicode character, allowing support for multiple languages.
Null and Embedded Nulls: Strings can be null and may also contain embedded null characters (\0).
Operator Overloading: Strings support operator overloading, such as + for concatenation and == for comparison.

String Class Properties: The String class has two properties as follows:

Chars: It is used to get the Char object at a specified position in the current String object.
Length: It is used to get the number of characters in the current String object. To know more about the string class properties please go to String Properties in C#.

Reading String from User-Input

A string can be read out from the user input. ReadLine() method of console class is used to read a string from user input.

Example:

// C# program to demonstrate Reading 
// String from User-Input
using System;

class Geeks 
{    
    // Main Method
    static void Main(string[] args)
    {

        Console.WriteLine("Enter the String");
    
        // Declaring a string object read_user 
        // and taking the user input using 
        // ReadLine() method
        String read_user = Console.ReadLine();
    
        // Displaying the user input
        Console.WriteLine("User Entered: " + read_user);

    }
    
}

Input:

Hello Geeks !

Output:

User Entered: Hello Geeks !

Different Ways to Create Strings

Method	Syntax / Example
Create a string from a literal	string str = “GeeksforGeeks”;
Create a string using concatenation	string str = str1 + “data”;
Create a string using a constructor	// Create a string from a character array char[] chars = { ‘G’, ‘E’, ‘E’, ‘K’, ‘S’ }; string str = new string(chars);
Create a string using a property or a method	// start and end are the index for str index string substr = str.Substring(start, end);
Create a string using formatting	string str = string.Format(“{0} {1} Cars color ” + “are {2}”, no.ToString(), cname, clr);

Example:

// Different Methods for Creating
// String in C#
using System;

public class GFG
{
      // Main Method
    static public void Main ()
    {
      
          // Creating String using string literal
        String str = "Geeks";
          Console.WriteLine("Method 1: " + str);
      
          // Creating String using concatenation
          String str2 = str + "ofGeeks";
          Console.WriteLine("Method 2: " + str2);
          
          // Creating a string using a constructor
          char[] chars = { 'G', 'E', 'E', 'K', 'S' };
        string str3 = new string(chars);
          Console.WriteLine("Method 3: " + str3);
          
          // Creating a string using a property or a method
          String s = "Geeks For Geeks";
          
          // Index of 
        int start = s.IndexOf(" ") + 1;
          int end = s.IndexOf(" ", start) - start;
          string str4 = s.Substring(start, end);
          Console.WriteLine("Method 4: " + str4);
      
          // Creating a string using formatting
          int i=1;
          int j=2;
          int sum= i + j;
          String str5 = string.Format("Addition of {0} with {1} is {2}"
                                    , i , j , sum );
          Console.WriteLine("Method 5: " + str5);
          
    }
}

Output

Method 1: Geeks
Method 2: GeeksofGeeks
Method 3: GEEKS
Method 4: For
Method 5: Addition of 1 with 2 is 3

C# String Operations

There are multiple String Operations which we can perform in String in C#. Let us demonstrate the operations using the example as mentioned below:

Example 1: For performing string operation of interpolation

using System;

public class GFG
{
      // Main Method
    static public void Main ()
    {
        string name = "GeeksforGeeks";
        
        // Interpolation is performed
        string res = $"{name} is the Organisation Name.";
        
        // Printing the String
        Console.WriteLine(res);
        Console.WriteLine("Length: " + res.Length);
    }
}

Output

GeeksforGeeks is the Organisation Name.
Length: 39

Example 2: for performing trim, replace and concatenate operation

using System;

public class GFG
{
    static public void Main ()
    {
        string first = " GeEks ";
        string second = " forGeeks ";
        
        // trim the String
        first=first.Trim();
        second=second.Trim();
        
        // Checking element at index 2 first
        Console.WriteLine("Element at index 2: " + first[2]);
        
        // replacing the element in String
        first=first.Replace("E","e");
        Console.WriteLine(first+second);
    }
}

Output

Element at index 2: E
GeeksforGeeks

In the above, two example we have explored many methods we are not full aware of so, there is a list of Methods associated with Strings in C# attached below.

Methods of C# String

Method	Description	Return Type	Example
IndexOf	Finds the index of the first occurrence of a specified character or substring.	Integer	text.IndexOf(“World”);
StartsWith	Checks if a string starts with a specified substring.	Boolean	text.StartsWith(“Hello”);
EndsWith	Checks if a string ends with a specified substring.	Boolean	text.EndsWith(“World!”);
ToUpper	Converts a string to uppercase.	String	text.ToUpper();
ToLower	Converts a string to lowercase.	String	text.ToLower();
Split	Splits a string into an array based on a specified delimiter.	String Array	fruits.Split(‘,’);
Join	Combines an array of strings into a single string with a specified delimiter.	String	string.Join(” – “, fruitArray);
Contains	Checks if a string contains a specified substring.	Boolean	text.Contains(“World”);
PadLeft	Pads a string with spaces or a specified character to a certain length.	String	text.PadLeft(20, ‘*’);
PadRight	Pads a string on the right with spaces or a specified character to a certain length.	String	text.PadRight(20, ‘*’);
Remove	Removes characters from a string starting at a specified index.	String	text.Remove(5, 7);
Insert	Inserts a string at a specified index.	String	text.Insert(5, ” Beautiful”);
Trim	Removes leading and trailing whitespaces.	String	text.Trim();
Replace	Replaces occurrences of a substring with another substring.	String	text.Replace(“fun”, “awesome”);

String Arrays

We can also create the array of string and assigns values to it. The string arrays can be created as follows:

String [] array_variable  =  new  String[Length_of_array]

Example:

// C# program for an array of strings
using System;

class Geeks 
{    
   // Main Method
   static void Main(string[] args)
   {
          String[] str_arr = new String[3];

        // Initialising the array of strings
        str_arr[0] = "Geeks";
        str_arr[1] = "For";
        str_arr[2] = "Geeks";

        // printing String array
        for(int i = 0; i < 3; i++) {
            Console.WriteLine("value at Index position " + i
                              + " is " + str_arr[i]);
        }

    }
}

Output

value at Index position 0 is Geeks
value at Index position 1 is For
value at Index position 2 is Geeks

String vs System.String

Aspects	`string` (Keyword)	`System.String` (Class)
Definition	Alias for `System.String`.	Fully qualified class name in .NET.
Performance	No difference in performance.	No difference in performance.
Usage	Commonly used for declaring variables, fields, and properties.	Used for accessing static methods or fully qualifying types.
Ease of Use	Provides a shorthand for writing code.	More verbose but functionally identical to `string`.
Accessing Methods	Methods are accessed via the `System.String` class.	Static methods like `String.Substring`, `String.IndexOf`, etc., are accessed directly.
Keyword or Class	C# keyword.	.NET class.

Note: In .NET, the text is stored as a sequential collection of the Char objects so there is no null-terminating character at the end of a C# string. Therefore a C# string can contain any number of embedded null characters (‘\0’).

JavaScript String Methods

Mithun Kumar

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Article Tags :

C# Strings

Key Characteristics of Strings

Reading String from User-Input

Input:

Output:

Different Ways to Create Strings

C# String Operations

Methods of C# String

String Arrays

String vs System.String

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