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C# Strings - GeeksforGeeks

Last Updated : 11 Jul, 2025

In C#, a string is a sequence of Unicode characters or an 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 about whether the string is a keyword, an object, or a class. So, let’s clear out this concept.

A string is represented by the 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 that both string and String 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 represent 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);
    }
}

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

• 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#.

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);

    }
    
}

Hello Geeks !

User Entered: Hello Geeks !

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);
      	
    }
}

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

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);
    }
}

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);
    }
}

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.

Method

Return Type

IndexOf

Integer

StartsWith

Boolean

EndsWith

Boolean

ToUpper

String

ToLower

String

Split

String Array

Join

String

Contains

Boolean

PadLeft

String

PadRight

String

Remove

String

Insert

String

Trim

String

Replace

String

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]);
        }

    }
}

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

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’). 

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