C# Class | C# Object and Class - c# - c# tutorial - c# net



C# Class

C# Class

C# Object

  • In C#, Object is a real world entity, for example, chair, car, pen, mobile, laptop etc.
  • In other words, object is an entity that has state and behavior. Here, state means data and behavior means functionality.
  • Object is a runtime entity, it is created at runtime.
  • Object is an instance of a class. All the members of the class can be accessed through object.
  • C# is an object-oriented language, program is designed using objects and classes in C#.
  • Let's see an example to create object using new keyword.
Class and Object

Class and Object

Syntax:

Student s1 = new Student();//creating an object of Student   
  • In this example, Student is the type and s1 is the reference variable that refers to the instance of Student class. The new keyword allocates memory at runtime.

C# Code Behind files

  • Splits visual design from functional development
  • This allows code developers to work separately from presentational designers
  • Code render blocks are placed in a separate C#, .cs file
  • This prevents "spaghetti" code and helps make pages more understandable

C# web pages - Code Behind files

  • sample.aspx contains page layout and static content
  • sample.aspx inherits from the class Sample
  • The definition of class Sample is in the Sample.cs file
learn c# - c# tutorial - c# code behind files - c# examples -  c# programs
learn c# - c# tutorial - c# code behind files - c# examples -  c# programs
learn c# - c# tutorial - c# code behind files - c# examples -  c# programs

C# Class

  • In C#, class is a group of similar objects. It is a template from which objects are created. It can have fields, methods, constructors etc.
  • A class is a construct that defines a collection of properties and methods in a single unit, which does not change during the execution of a program.
  • Let's see an example of C# class that has two fields only.
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c# class vs struct :

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c# struct vs c++ struct :

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Syntax:

public class Student  
{  
int id;//field or data member   
String name;//field or data member  
}  
 classes objects

C# Object and Class Example

  • Let's see an example of class that has two fields: id and name. It creates instance of the class, initializes the object and prints the object value.
using System;  
   public class Student  
    {  
        int id;//data member (also instance variable)    
        String name;//data member(also instance variable)    
         
    public static void Main(string[] args)  
        {  
            Student s1 = new Student();//creating an object of Student    
            s1.id = 101;  
            s1.name = "Sonoo Jaiswal";  
            Console.WriteLine(s1.id);  
            Console.WriteLine(s1.name);  
  
        }  
    }  
Class and Object

Class and Object

C# examples - Output :

101
Sonoo Jaiswal

C# Class Example 2: Having Main() in another class

  • Let's see another example of class where we are having Main() method in another class. In such case, class must be public.
using System;  
   public class Student  
    {  
        public int id;   
        public String name;  
   }  
   class TestStudent{  
       public static void Main(string[] args)  
        {  
            Student s1 = new Student();    
            s1.id = 101;  
            s1.name = "Sonoo Jaiswal";  
            Console.WriteLine(s1.id);  
            Console.WriteLine(s1.name);  
  
        }  
    }  

C# examples - Output :

101
Sonoo Jaiswal

C# Class Example 3: Initialize and Display data through method

  • Let's see another example of C# class where we are initializing and displaying object through method.
using System;  
   public class Student  
    {  
        public int id;   
        public String name;  
        public void insert(int i, String n)  
        {  
            id = i;  
            name = n;  
        }  
        public void display()  
        {  
            Console.WriteLine(id + " " + name);  
        }  
   }  
   class TestStudent{  
       public static void Main(string[] args)  
        {  
            Student s1 = new Student();  
            Student s2 = new Student();  
            s1.insert(101, "Ajeet");  
            s2.insert(102, "Tom");  
            s1.display();  
            s2.display();  
  
        }  
    }  

C# examples - Output :

101 Ajeet
102 Tom

C# Class Example 4: Store and Display Employee Information

using System;  
   public class Employee  
    {  
        public int id;   
        public String name;  
       public float salary;  
        public void insert(int i, String n,float s)  
        {  
            id = i;  
            name = n;  
            salary = s;  
       }  
        public void display()  
        {  
            Console.WriteLine(id + " " + name+" "+salary);  
        }  
   }  
  class TestEmployee{  
       public static void Main(string[] args)  
        {  
            Employee e1 = new Employee();  
           Employee e2 = new Employee();  
            e1.insert(101, "Sonoo",890000f);  
            e2.insert(102, "Mahesh", 490000f);  
            e1.display();  
            e2.display();  
  
        }  
    }  

C# examples - Output :

19Y4NSiG8kkzwWjMD17euEaQ5PErpwxWkP

c# Access Modifiers :

  • public :
    • public is the most common access specifier in C# .
    • It can be access from anywhere, that means there is no restriction on accessibility.
    • The scope of the accessibility is inside class as well as outside.
    • The type or member can be accessed by any other code in the same assembly or another assembly that references it.
  • private :
    • The scope of the accessibility is limited only inside the classes or struct in which they are declared.
    • The private members cannot be accessed outside the class and it is the least permissive access level.
  • protected :
    • The scope of accessibility is limited within the class or struct and the class derived (Inherited )from this class.
  • internal :
    • The internal access modifiers can access within the program that contain its declarations and also access within the same assembly level but not from another assembly.
  • protected internal :
    • Protected internal is the same access levels of both protected and internal.
    • It can access anywhere in the same assembly and in the same class also the classes inherited from the same class .
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    c# access specifiers

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    c# public protected private access specifiers


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