Chapter: 4 String

By Haitomns G

4.1    Introduce the strings, its usages and functions

C# supports a predefined reference type known as string. We can use string to declare string type objects. Remember, when we declare a string using string type, we are in fact declaring the object to be of type System.String, one of the built-in types provided by the .NET Framework. A string type is therefore a System.String type as well.

Usage of string

Most programming languages have a data type called a string, which is used for data values that are made up of ordered sequences of characters, such as “hello world”. A string can contain any sequence of characters, visible or invisible, and characters may be repeated. The main usage of string is to store a sequence of characters together in a variable.

4.2    Demonstrate the creation of a string object

We can create immutable strings using string or String objects in a number of ways.

  • Assigning string literals
  • Copying from one object to another
  • Concatenating two objects
  • Reading from the keyboard
  • Using ToString method.

Code:

using System; 

namespace CsharpString { 

  class Test {

    public static void Main(string [] args) {

      // create string

      string str1 = “C# Programming”;

      string str2 = “Microsoft”;

      // print string

      Console.WriteLine(str1);

      Console.WriteLine(str2);

      Console.ReadLine();

    }

  }

}

                Output:

C# Programming

Microsoft

4.3    Demonstrate the methods of string class and deduce its usages

4.4    Introduce to string functions and examine the usage of functions

String objects are immutable, meaning that we cannot modify the characters contained in them. However, since the string is an alias for the predefined System.String class in the Common Language Runtime (CLR), there are many built-in operations available that work with strings. All operations produce a modified version of the string rather than modifying the string on which the method is called.

Code:

using System;

class HelloWorld

{

    static void Main()

    {

        string str = “Hello World”;

        Console.WriteLine(str.Length);

        Console.WriteLine(str.ToUpper());

        Console.WriteLine(str.ToLower());

        Console.WriteLine(str.Trim());

        Console.WriteLine(str.Replace(“World”, “C#”));

        Console.WriteLine(str.Substring(6, 5));

        string[] words = str.Split(‘ ‘);

        foreach (string word in words)

        {

            Console.WriteLine(word);

        }

        Console.WriteLine(str.IndexOf(“World”));

        Console.WriteLine(str.LastIndexOf(“World”));

        Console.WriteLine(str.Insert(6, “C#”));

        Console.WriteLine(str.Remove(6, 3));

        Console.WriteLine(str.PadLeft(20));

        Console.WriteLine(str.PadRight(20));

        char[] chars = str.ToCharArray();

        foreach (char ch in chars)

        {

            Console.WriteLine(ch);

        }

    }

}

                Output:

                                11HELLO WORLD

hello world

Hello World

Hello C#World

Hello

World

6

6

Hello C#World

Hello ld

         Hello World

Hello World        

H

e

l

l

o

W

o

r

l

d

            Reading from the Keyboard

It is possible to read a string value interactively from the keyboard and assign it to a string object.

string s = Console.ReadLine();

On reaching this statement, the computer will wait for a string of characters to be entered from the keyboard. When the ‘return key’ is pressed, the string will be read and assigned to the string object s.

Haitomns G. is a desktop, android, and web developer based in Nepal. He has worked on building several websites, apps, and softwares for clients and independent projects. He is experienced in C, C++, C#, Java, Python, SQL, HTML, CSS, PHP, and JavaScript.

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