C# - Strings

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In C#, you can use strings as array of characters, However, more common practice is to use the string keyword to declare a string variable. The string keyword is an alias for the System.String class.

Creating a String Object

You can create a string object using one of the following methods −

• By assigning a string literal to a String variable

• By using a String class constructor

• By using the string concatenation operator (+)

• By retrieving a property or calling a method that returns a string

• By calling a formatting method to convert a value or an object to its string representation

Example to Create a String Object

The following example demonstrates all the methods listed above:

using System;
namespace StringApplication {
   class Program {
      static void Main(string[] args) {
         // Creating a string using a string literal and concatenation
         string fname, lname;
         fname = "Rowan";
         lname = "Atkinson";

         char[] letters = {'H', 'e', 'l', 'l', 'o'};
         string[] sarray = {
            "Hello",
            "From",
            "Tutorials",
            "Point"
         };

         string fullname = fname + " " + lname;
         Console.WriteLine("Full Name: {0}", fullname);

         // Creating a string using a character array
         string greetings = new string(letters);
         Console.WriteLine("Greetings: {0}", greetings);

         // Joining an array of strings
         string message = String.Join(" ", sarray);
         Console.WriteLine("Message: {0}", message);

         // Formatting method to convert a value
         DateTime waiting = new DateTime(2012, 10, 10, 17, 58, 1);
         string chat = String.Format("Message sent at {0:t} on {0:D}", waiting);
         Console.WriteLine("Message: {0}", chat);
      }
   }
}

When the above code is compiled and executed, it produces the following result −

Full Name: Rowan Atkinson
Greetings: Hello
Message: Hello From Tutorials Point
Message: Message sent at 5:58 PM on Wednesday, October 10, 2012

Creating a String

You can create a string in C# using string literals or the String class.

Example

In the following example, we are creating a simple string and printing it.

using System;
namespace StringApplication {
   class StringProg {
      static void Main(string[] args) {
         string message = "Hello, C#!";
         Console.WriteLine(message);
      }
   }
}

When the above code is compiled and executed, it produces the following result −

Hello, C#!

Finding String Length

You can find the length of a string using the Length property.

Example

In the following example, we are finding and printing the length of a given string.

using System;
namespace StringApplication {
   class StringProg {
      static void Main(string[] args) {
         string str = "C# Programming";
         int length = str.Length;
         Console.WriteLine("Length of the string: " + length);
      }
   }
}

When the above code is compiled and executed, it produces the following result −

Length of the string: 14

Iterate Over String Characters

You can iterate over each character in a string using a foreach loop.

Example

In the following example, we are iterating through each character of a string and printing them separately.

using System;
namespace StringApplication {
   class StringProg {
      static void Main(string[] args) {
         string str = "C# by TP";
         
         foreach (char ch in str) {
            Console.WriteLine(ch);
         }
      }
   }
}

When the above code is compiled and executed, it produces the following result −

C
#

b
y
 
T
P

Comparing Strings

You can compare two strings using the String.Compare method or the equality operator.

Example

In the following example, we are comparing two strings and displaying whether they are equal or not.

using System;
namespace StringApplication {
   class StringProg {
      static void Main(string[] args) {
         string str1 = "Hello";
         string str2 = "World";
         
         if (String.Compare(str1, str2) == 0) {
            Console.WriteLine("Strings are equal.");
         } else {
            Console.WriteLine("Strings are not equal.");
         }
      }
   }
}

When the above code is compiled and executed, it produces the following result −

Strings are not equal.

Checking for a Substring

You can check if a string contains another string using the Contains method.

Example

In the following example, we are checking if a given substring exists in a string.

using System;
namespace StringApplication {
   class StringProg {
      static void Main(string[] args) {
         string str = "Welcome to C# programming";
         
         if (str.Contains("C#")) {
            Console.WriteLine("The sequence 'C#' was found.");
         }
      }
   }
}

When the above code is compiled and executed, it produces the following result −

The sequence 'C#' was found.

Getting a Substring

You can extract a part of a string using the Substring method.

Example

In the following example, we are extracting a part of a string and displaying it:

using System;
namespace StringApplication {
   class StringProg {
      static void Main(string[] args) {
         string str = "C# Programming Language";
         Console.WriteLine(str);
         string substr = str.Substring(3, 11);
         Console.WriteLine(substr);
      }
   }
}

When the above code is compiled and executed, it produces the following result −

Programming

Joining Strings

You can join multiple strings using the String.Join method.

Example

In the following example, we are joining an array of strings using a newline character:

using System;
namespace StringApplication {
   class StringProg {
      static void Main(string[] args) {
         string[] lines = new string[] {
            "C# is a modern",
            "Object-oriented",
            "Programming language"
         };
         
         string result = String.Join("\n", lines);
         Console.WriteLine(result);
      }
   }
}

When the above code is compiled and executed, it produces the following result −

C# is a modern
Object-oriented
Programming language

Handling Strings Using StringBuilder

StringBuilder helps to modify strings because regular strings cannot be changed directly. You can use StringBuilder to add, insert, or replace text without creating new string copies.

Example: Using StringBuilder

The following example demonstrates how to use StringBuilder to modify strings:

using System;
using System.Text;

class Program {
    static void Main() {
        StringBuilder sb = new StringBuilder("Hello");
        sb.Append(" World!");
        sb.Insert(6, "C# ");
        sb.Replace("World", "Everyone");

        Console.WriteLine(sb.ToString());
    }
}

When executed, this program outputs:

Hello C# Everyone!

Properties of the String Class

The String class has the following two properties −

Methods of the String Class

The String class has numerous methods that help you in working with the string objects. The following table provides some of the most commonly used methods −

In this chapter, we have summarized key methods of the string class commonly used in C# programming. For the complete list of methods and String class constructors, visit the MSDN library.