In C#, a 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 represented by a class System.String.

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 the String object in memory can be 2GB or about 1 billion characters.

Characteristics of String Class:

• System.String class is immutable, i.e once created its state cannot be altered.
• With the help of length property, it provides the total number of characters present in the given string.
• String objects can include a null character which counts as the part of the string’s length.
• It provides the position of the characters in the given string.
• It allows empty strings. Empty strings are the valid instance of String objects that contain zero characters.
• A string that has been declared but has not been assigned a value is null. Attempting to call methods on that string throws a NullReferenceException.
• It will also supports searching strings, comparison of string, testing of equality, modifying the string, normalization of string, copying of strings, etc.
• It’s also provides several ways to create strings like using a constructor, using concatenation, etc.

Constructor

Example:

// C# program to demonstrate the creation
// of string using the constructor
using System;
class Tech {
  
    // Main Method
    public static void Main()
    {
        char[] chars = { 'T', 'E', 'C', 'H', 'A' };
  
        // Create a string from a character array.
        string str1 = new string(chars);
        Console.WriteLine(str1);
  
        // Create a string that consists of
        // a character repeated 5 times.
        string str2 = new string('E', 5);
        Console.WriteLine(str2);
    }
}

Output:

TECHA
EEEEE

Properties

Example:

// C# program to demonstrate the
// String Class Properties
using System;
  
class Tech {
   
    // Main Method
    public static void Main()
    {
        string str = "TechforTech";
          
        // using Chars[Int32] & Length property
        for (int i = 0; i <= str.Length - 1; i++)
            Console.Write("{0} ", str[i]);
    }
}

Output:

T e c h f o r T e c h

Method

Example:

// C# program to illustrate
// String class methods
using System;
   
class TAS {
      
    static void copymethod()
    {
        string str1 = "TechforTech";
        string str2 = "tech";
        Console.WriteLine("Original Strings: str1 = "
                              + "'{0}' and str2 ='{1}'",
                          str1, str2);
   
        Console.WriteLine("");
   
        Console.WriteLine("After Copy method");
        Console.WriteLine("");
   
        // using the Copy method
        // to copy the value of str1
        // into str2
        str2 = String.Copy(str1);
   
        Console.WriteLine("Strings are str1 = "
                              + "'{0}' and str2='{1}'",
                          str1, str2);
    }
      
   
    // Main method
    static public void Main()
    {
   
        // variables
        string str1 = "techfortech";
        string str2 = "techfortech";
   
        bool result;
   
        // Compare(string, string) method return true
        // because the given strings are equal
        result = String.Compare(str1, str2) == 0;
   
        Console.WriteLine("Result of Compare Method: " +result);
          
        // calling method
        copymethod();
    }
}

Output:

Result of Compare Method: True
Original Strings: str1 = 'TechforTech' and str2 ='tech'

After Copy method

Strings are str1 = 'TechforTech' and str2='TechforTech'

Operators

Example:

// C# program to illustrate the
// Equality and Inequality operator
using System;
  
class TAS {
  
    // Main Method
    public static void Main(string[] args)
    {
        string s1 = "WelcomeToTech";
        string s2 = "WelcomeToTech";
        bool result1, result2;
  
        // Equality operator return true
        // as both string are equal
        result1 = s1 == s2;
  
        // Inequality operator return false
        // as both string are equal
        result2 = s1 != s2;
  
        Console.WriteLine(result1);
        Console.WriteLine(result2);
    }
}

Output:

True
False