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Week 7: Inheritance in C#

⁠

1. Understanding Inheritance

Definition: Inheritance allows a class (derived class) to acquire properties and behaviors (methods) from another class (base class).
Base Class: The class that provides the inherited members.
Derived Class: The class that inherits from the base class.
Syntax:
csharp
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class DerivedClass : BaseClass
{
// Additional methods and fields
}

⁠

2. Accessing Base Class Members

Inherited Members: A derived class has access to public and protected members of its base class.
Example:
csharp
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class Animal
{
public void Eat() { Console.WriteLine("Eating..."); }
}

class Dog : Animal
{
public void Bark() { Console.WriteLine("Barking..."); }
}

// Usage
Dog dog = new Dog();
dog.Eat(); // Inherited from Animal
dog.Bark(); // Specific to Dog

⁠

3. Virtual Methods and Overriding

Virtual Method: A method in the base class that can be overridden in the derived class.
Use the virtual keyword in the base class and override in the derived class.
Syntax:
csharp
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class Animal
{
public virtual void Speak() { Console.WriteLine("Animal Sound"); }
}

class Dog : Animal
{
public override void Speak() { Console.WriteLine("Woof"); }
}

Calling Base Implementation: Use base.MethodName() in the derived class to call the base class’s implementation.
⁠

4. Abstract Classes

Abstract Class: Cannot be instantiated and may contain abstract methods (methods without implementation).
Abstract Method: Must be implemented in any derived non-abstract class.
Syntax:
csharp
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abstract class Animal
{
public abstract void Speak();
}

class Dog : Animal
{
public override void Speak() { Console.WriteLine("Woof"); }
}

⁠

5. The Object Class

All Classes Inherit from Object: This base class provides common methods such as ToString(), Equals(), and GetHashCode(), which can be overridden for custom behavior.
⁠

6. Polymorphism Through Inheritance

Polymorphism: The ability of different derived classes to be treated as instances of their base class, each implementing its version of a method.
Example:
csharp
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Animal myAnimal = new Dog(); // Base type reference, derived type object
myAnimal.Speak(); // Calls Dog’s implementation of Speak()

⁠

7. Inheritance Hierarchies and Class Diagrams

Inheritance Hierarchies: Shows the structure of how classes relate in inheritance, with base classes at the top.
UML Class Diagrams:
Arrow Notation: A solid line with a hollow triangle pointing to the base class represents inheritance in UML diagrams.
⁠

Quick Study Tips for MCQs

Distinguish Access Levels: Know how public, protected, and private affect inheritance.
Virtual and Override Keywords: Understand when to use these for polymorphic behavior.
Abstract Classes: Recognize that abstract methods require implementation in derived classes.
Object Class Methods: Remember key methods (ToString(), Equals()) that can be overridden.
⁠
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