Implementing interfaces in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Implementing interfaces

Define Interface

↓

Create Class

↓

Implement Interface Methods

↓

Create Object of Class

↓

Call Interface Methods

↓

Use Polymorphism if needed

↓

End

This flow shows how you define an interface, implement it in a class, create an object, and call the interface methods.

Execution Sample

C Sharp (C#)

using System;

interface IAnimal {
    void Speak();
}

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

class Program {
    static void Main() {
        Dog dog = new Dog();
        dog.Speak();
    }
}

This code defines an interface IAnimal with Speak method, implements it in Dog class, creates a Dog object, and calls Speak.

Execution Table

Step	Action	Evaluation	Result
1	Define interface IAnimal with Speak()	Interface created	IAnimal interface ready
2	Create class Dog implementing IAnimal	Dog class created	Dog class ready with Speak() method
3	Implement Speak() in Dog	Method implemented	Speak() prints 'Woof!'
4	Create Dog object dog	dog = new Dog()	dog object created
5	Call dog.Speak()	dog.Speak() called	Output: Woof!
6	End of execution	No more code	Program ends

💡 Program ends after calling Speak() method on dog object

Variable Tracker

Variable	Start	After Step 4	After Step 5	Final
dog	null	Dog object created	Dog object exists	Dog object exists

Key Moments - 3 Insights

Why do we need to implement all methods of the interface in the class?

Because the interface defines a contract. As shown in step 3 of execution_table, the class must provide the method implementation or it will cause a compile error.

Can we create an object of the interface directly?

No, interfaces cannot be instantiated. Step 4 shows we create an object of the class that implements the interface, not the interface itself.

What happens when we call the interface method on the class object?

The class's implementation runs. Step 5 shows calling dog.Speak() runs Dog's Speak method printing 'Woof!'.

Visual Quiz - 3 Questions

Look at the execution table, what is the output when dog.Speak() is called at step 5?

A "Meow!"

B No output

C "Woof!"

D Compile error

💡 Hint

Check the Result column at step 5 in the execution_table.

At which step is the Dog object created?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look at the Action column for object creation in the execution_table.

If the Dog class did not implement Speak(), what would happen?

A Program runs normally

B Compile error occurs

C Speak() prints nothing

D Interface method is called by default

💡 Hint

Refer to key_moments about implementing all interface methods.

Concept Snapshot

interface InterfaceName {
    void MethodName();
}

class ClassName : InterfaceName {
    public void MethodName() { /* implementation */ }
}

- Interfaces define method signatures.
- Classes must implement all interface methods.
- Cannot create interface objects directly.
- Use class objects to call interface methods.

Full Transcript

This example shows how to implement interfaces in C#. First, we define an interface IAnimal with a method Speak. Then, we create a class Dog that implements IAnimal and provides the Speak method. We create an object dog of type Dog and call dog.Speak(), which prints 'Woof!'. The execution table traces each step from defining the interface to calling the method. The variable tracker shows the dog object is created and used. Key moments clarify why all interface methods must be implemented, that interfaces cannot be instantiated, and how calling the method runs the class's implementation. The quiz questions test understanding of output, object creation step, and consequences of missing method implementation. The snapshot summarizes syntax and rules for implementing interfaces in C#.