Class in C# | Chapter 11

Class

A class represents a blueprint of an object.

• Currently, we know some basic data types:
  • For representing numbers, we use types like int, long, byte, decimal, etc.
  • For representing words, we use string or arrays of characters (char[]).
  • For storing collections of numbers, we use arrays (int[], float[], etc.).

However, what about storing complex objects like Person, Planet, etc.?

• For example, a Person object might have properties like Name (a string), Age (an integer), and methods like IsCoding().

From the diagram above, we see that a class named Person encapsulates a contextual representation driven by developers. It defines properties and behaviors specific to a person, allowing us to model and work with such complex entities in code.

Requirement

To proceed with this, you’ll need Visual Studio Community Edition for easier coding with auto-suggestion. Let’s create a brand new console project in Visual Studio.

Understanding Class Syntax in C#

In C#, we represent a Person using the class keyword, encapsulating related properties and methods inside the class body. Below is a basic representation of a Person in terms of a class:

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public class Person
{
    public string Name;
    public string From = "Earth";
    public int Age;

    public void IsWalking()
    {
        // Method body will be added later
    }
}

Now, let me explain each line step by step:

• public: This keyword in C# determines the accessibility level of something (class, field, or method). Here, it allows the Person class, Name field, From field, and IsWalking method to be accessible from other classes.
• We’ll delve deeper into programming concepts as you gain more confidence, or you’ll learn about them automatically as we progress.

Now we know that what class is and how to represent real thing in form of class

Question Now is How to use this class ?

In C#, we create an instance or object of a class and then utilize it. Let’s clarify what these terms mean:

• Instance/Object: Imagine you’re an artist.

  • Your task is to download the image below:

  

  • Once downloaded, your next task is to fill the CFD (Codefrydev 😁) with any color your artistic mind suggests.

  • Here’s how my programmer mind sees it:

  

• Downloading the image is akin to creating an instance or object.

• You can then manipulate the downloaded image as you wish, which won’t affect the version available on the website.

• Filling the color is like assigning different values to the fields or properties of an instance in programming.

Create Instance Syntax

• To create an instance of the Person class in C#, follow the syntax:

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Person myself = new Person();

Here, myself is an instance of the Person class, possessing all the characteristics defined within the class by default.

Visual Representation

• The Name field is null because it hasn’t been assigned a value in the class definition.
• The From field has the value "Earth" because it is initialized to this value in the class.

Now we know the syntax of how to create instance of class

Question now comes in mind that how do we modify ?

If you type myself. and use IntelliSense in Visual Studio, you will see options related to the fields and methods defined in the Person class. Here’s how you can modify the code to assign values to the object’s fields:

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myself.Age = 0;
myself.From = "CodefryDev Website";
myself.Name = "CodefryDev User";

• you will have object with modified value as per above code.

• you can view in Visual Studio by using below code and pressing 5 key

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Console.WriteLine("From {0}",myself.From);
Console.WriteLine("Name {0}", myself.Name);
Console.WriteLine("Age {0}", myself.Age);

• it will output somting like this

• using Terminal Command

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dotnet run --property WarningLevel=0

Modification in class

changes in the class method IsWalking

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public class Person
{
    public string Name;
    public string From ="Earth";
    public int Age;

    public void IsWalking()
    {
        Console.WriteLine("No I Learing on CFD");
    }
} 

• Calling a method in C# involves using the instance name followed by a period (.), the method name, opening and closing parentheses (), and ending with a semicolon ;. This syntax executes the behavior defined within the method.

You can call this method on an instance of the Person class like this:

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myself.IsWalking();

• Source code Upto this point
• you can use new c# syntax Person myself = new(); instead of Person myself = new Person();

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// creating instance of object
Person myself = new Person(); 

// assigning value
myself.Age = 0;
myself.From = "CodefryDev Website";
myself.Name = "CodefryDev User";
// printing to console
Console.WriteLine("From {0}",myself.From);
Console.WriteLine("Name {0}", myself.Name);
Console.WriteLine("Age {0}", myself.Age);
myself.IsWalking();

• now Run the application an you will have following.

Another Object

• Create another instance of the class Person and observe its default values.
• Guess if the value will be the same as myself or something else.
• Let’s solve this mystery by creating another instance of the class.

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Person friend = new Person();

• Surprisingly, its value is not the same as myself. Wait, what? Why?

• Okay, let me explain using the analogy of downloading an image.

• If creating an instance is like downloading the image again,

• Obviously, no matter how many times you modify or paint it with different colors, it’s still the same downloaded image.

• A similar concept applies to modifying object instances as well.

• Now, modify the object value of friend with a different value and see what happens.

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friend.Age = 1;
friend.From = "Mars";
friend.Name = "Terminal";

• Now this data is held by a different object.

• Using the terminal:

• Source code upto this point

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Person myself = new Person();
myself.Age = 0;
myself.From = "CodefryDev Website";
myself.Name = "CodefryDev User";


Person freind = new Person();
freind.Age = 1;
freind.From = "Mars";
freind.Name = "Terminal";

Console.WriteLine("Freind Object Holding value");
Console.WriteLine("From {0}", freind.From);
Console.WriteLine("Name {0}", freind.Name);
Console.WriteLine("Age {0}", freind.Age);

Console.WriteLine("myself Object Holding value");
Console.WriteLine("From {0}",myself.From);
Console.WriteLine("Name {0}", myself.Name);
Console.WriteLine("Age {0}", myself.Age);

More about Object/Instance

Coming back to the analogy of downloading an image on your PC:

• Whenever you download an image, it will be stored somewhere on your PC.
• Each image will have a unique name in its specific folder.
• This means no two images can have the same name in the same folder.
• Each image will take up some space.
• Each downloaded image will have separate properties from other images.
• See the image below for demonstration:

• another image

• Similar to this, each instance of a class will:
  • Have a separate location in memory where it is stored.
  • Occupy a specific amount of space on your PC.
  • Cannot have the same name as another instance.
  • A folder is analogous to a namespace in C#.

For more information about classes, please refer to the Official documentation.

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