C#

• Introduction
• Getting Output
• Datatype
• Variable Declaration
• Operator
• string concatenation
• Converting Datatype
• Getting input from user
• Working on Angles
• Escape Sequence
• Conditional Statements
• If statement
• Switch statement
• Types of Error
• Exception Handling
• Loop
• While Loop
• For Loop
• Do While Loop
• Array
• Foreach Loop
• Multi dimensional array
• Nested Loop
• Jump Statment
• String Handling Function
• Methods or Functions
• Passing Parameter
• Method Overloading
• Void Function
• Returning Function
• Class
• Creating New Instance
• Static Keyword
• Constructor
• Constructor Overloading
• Destructor
• Inheritance
• Multi Level Inheritance
• Multiple Inheritance
• Sealed Class
• Partial Class
• Upcasting
• Abstract Class
• Interface
• Ref,Out,In Parameters
• Field Vs Property
• Struct
• DateTime
• Enum
• Namespace
• Dynamic Link Library(DLL)
• Collections
• File Handling
• Excel handling

Multi Level Inheritance

When we create a child class which inherited from another child class or in simple word if a class is created by using another child class then this type of implementation is called as Multilevel Inheritance.

Syntax
class Class2 : Class1 {
    //Fields and methods
}
class Class3 : Class2 {
    //Fields and methods
}

In the above syntax, Class1 is the parent class of Class2, Class2 is the parent class of Class3. Now the relation between class1 and Class3 is, Class1 is the the Grand parent class of Class3 or Class3 is the Grand child class of Class1. This grand parent and grand child concept is nothing but Multi level inheritance.

CODE

EG 1 . Creating a class called Rectangle2D and inheriting to Rectangle3D class then creating a new class called Rectangle4D and inheriting Rectangle3D class

class Rectangle2D {
    public double length, width;
    public double Area() {
        return length * width;
    }
    public double Perimeter() {
        return 2 * (length+width);
    }
}

//Inheriting Rectangle2D to Rectangle3D
class Rectangle3D : Rectangle2D {
    public double height;
    public double Volume() {
        return length * width * height;
    }
}

//Inheriting Rectangle3D to Rectangle4D
class Rectangle4D : Rectangle3D {
    public void sampleMethod() {
        Console.WriteLine(length + width + height + Area() + Volume()) ;
    }
}


CODE EXPLANATION
In the above code, we can see 3 classes called Rectangle2D, Rectangle3D and Rectangle4D. About 2 dimensional rectangle and 3 dimensional rectangle we already discussed in Inheritance concept. Here we created one more class called Rectangle4D which holds fields and methods of 4 dimensional rectangle. Theoretically and also practically 4 dimensional is not possible, here it is taken only for Example purpose. 4 dimensional rectangle is going to have all the fields and methods of Rectangle2D and Rectangle3D. Since Rectangle3D is the child class and Rectangle2D is the parent class, if we inherit Rectangle3D to Rectangle4D, Rectangle4D will become the child class of Rectangle3D and grand child class of Rectangle2D. Now Rectangle4D can access all the fields and methods from its parent Rectangle3D and from its grand parent Rectangle2D.