Class and Object

To overcome the drawbacks of procedural languages, the object-oriented language is introduced and
this provides additional benefits like the security and reusability of code.

Eg: C++, C#, Java, etc.

So in the object-oriented programming language, the members like variables and functions are kept under a
container known as a class. This class provides security for the content of the class.

Class:

The Class is a user-defined data type similar to the structure in procedural languages.
The structure can contain only variables in it whereas a Class can contain both variables and functions.

Object:

A copy of a complex type like class or structure is called an Object.
A data type cannot be used directly, if we want to use then we need to create a copy of it.

int = 5; // This is invalid.
int p = 5; // This is valid.

Similarly, any user-defined type like class or structure cannot be used directly, we need to create a copy
of that class which is an object, and consume the members of the class with the object.

Class MySample
{
//Function members
}
Main Method()
{
//Create object of class MySample
//Access the members of the class using the object.
}

Static Class:

A Class that is declared by using a static modifier is known as a static class. A static class can contain only
static members in it.
We cannot create an object to a static class because it contains only static members. These static methods
are accessed by using the class name.

Syntax:

static class XX
{

}

Example:

using System;
namespace SampleProgram {
static class MySample {
public static string greet = “Hello World”;
public static void GreetInfo() {
Console.WriteLine("Hello !! ");
}
}
class MainClass {
public static void Main(string[] args) {
MySample.GreetInfo();
Console.WriteLine(MySample.greet);
}
}
}

The output will be:

Hello!!
Hello World

Sealed Class:

The class which cannot be extended further is called Sealed Class. These classes use the sealed modifier.
So the sealed classes cannot participate in inheritance.

Syntax:

sealed class XX
{

}

Example:

using System;
namespace SampleProgram {
sealed class MySample {
public string greet = “Hello World”;
public void GreetInfo() {
Console.WriteLine( "Hello !! ");
}
}
class MainClass: MySample // Cannot inherit the sealed class
{
public static void Main(string[] args) {

}
}
}

The output will be:

Error CS0509 cannot derive from sealed type ‘MySample

Class and Object

Class:

Object:

Static Class:

Sealed Class:

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Class and Object

Class:

Object:

Static Class:

Sealed Class:

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