Multiple interface implementation in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Multiple interface implementation

Define Interface A

↓

Define Interface B

↓

Create Class implementing A and B

↓

Implement methods from A and B

↓

Create object of Class

↓

Call methods from both interfaces

↓

Use combined behavior

This flow shows how a class can implement multiple interfaces by defining all required methods, then using an object to access all interface behaviors.

Execution Sample

C Sharp (C#)

using System;
interface IA { void MethodA(); }
interface IB { void MethodB(); }
class MyClass : IA, IB {
  public void MethodA() { Console.WriteLine("A"); }
  public void MethodB() { Console.WriteLine("B"); }
}
class Program {
  static void Main() {
    var obj = new MyClass();
    obj.MethodA(); obj.MethodB();
  }
}

This code defines two interfaces and a class that implements both, then calls their methods.

Execution Table

Step	Action	Evaluation	Result
1	Define interface IA	Interface IA with MethodA declared	IA ready
2	Define interface IB	Interface IB with MethodB declared	IB ready
3	Define class MyClass implementing IA and IB	Class must implement MethodA and MethodB	MyClass ready
4	Implement MethodA in MyClass	MethodA prints 'A'	MethodA implemented
5	Implement MethodB in MyClass	MethodB prints 'B'	MethodB implemented
6	Create object obj of MyClass	obj is instance of MyClass	obj created
7	Call obj.MethodA()	Calls MethodA	Output: A
8	Call obj.MethodB()	Calls MethodB	Output: B
9	End of execution	All interface methods called	Program ends

💡 All interface methods implemented and called, program ends normally

Variable Tracker

Variable	Start	After 6	After 7	After 8	Final
obj	null	MyClass instance	MyClass instance	MyClass instance	MyClass instance

Key Moments - 2 Insights

Why must MyClass implement all methods from both interfaces?

Because in row 3 of execution_table, the class declares it implements IA and IB, so it must provide all methods declared in both interfaces to compile.

Can we call MethodA and MethodB on obj directly?

Yes, as shown in rows 7 and 8, obj is a MyClass instance that implements both interfaces, so both methods are accessible.

Visual Quiz - 3 Questions

Look at the execution_table at step 4, what does MethodA do?

A Prints 'A' to the console

B Prints 'B' to the console

C Throws an error

D Does nothing

💡 Hint

Check the 'Evaluation' and 'Result' columns at step 4 in execution_table

At which step is the object 'obj' created?

A Step 3

B Step 7

C Step 6

D Step 1

💡 Hint

Look for the action mentioning 'Create object obj' in execution_table

If MyClass did not implement MethodB, what would happen?

A Program runs normally

B Compile-time error occurs

C MethodB calls print 'A'

D Runtime error occurs

💡 Hint

Refer to key_moments about implementing all interface methods

Concept Snapshot

Multiple interface implementation in C#:
- Use class : Interface1, Interface2
- Implement all interface methods
- Create object of class
- Call methods from all interfaces
- Enables combining behaviors from multiple sources

Full Transcript

This example shows how a class in C# can implement multiple interfaces by listing them separated by commas after the colon. The class must provide all methods declared in each interface. We define two interfaces IA and IB, each with one method. Then we create MyClass implementing both. It provides MethodA and MethodB. We create an object of MyClass and call both methods, printing 'A' and 'B'. This demonstrates how multiple interface implementation allows a class to combine behaviors from different contracts.