Publisher-subscriber execution model in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the Publisher-Subscriber execution model?

It is a design pattern where a publisher sends messages or events without knowing who will receive them, and subscribers listen for these messages to react accordingly.

beginner

In C#, what keyword is commonly used to declare events in the Publisher-Subscriber model?

The event keyword is used to declare events that subscribers can listen to.

beginner

How does a subscriber register to receive notifications from a publisher in C#?

A subscriber adds a method to the publisher's event using the += operator to subscribe.

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What happens when a publisher raises an event in the Publisher-Subscriber model?

All subscriber methods attached to that event are called automatically to handle the event.

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Why is the Publisher-Subscriber model useful in programming?

It helps decouple components, so publishers and subscribers don't need to know about each other directly, making code easier to maintain and extend.

In the Publisher-Subscriber model, who knows about the subscribers?

A Subscribers know about each other

B Only the publisher knows about the subscribers

C Neither publisher nor subscribers know about each other

D Only the subscribers know about the publisher

Subscribers know about the publisher because they subscribe to its events, but the publisher does not know the subscribers directly.

Which C# operator is used by subscribers to attach their methods to a publisher's event?

A +=

B -=

C ==

D =>

The '+=' operator is used to subscribe a method to an event.

What keyword declares an event in a C# publisher class?

A event

B publish

C subscribe

D delegate

The 'event' keyword declares an event that subscribers can listen to.

What is the main benefit of using the Publisher-Subscriber model?

A Tight coupling between components

B Faster execution speed

C Decoupling components for easier maintenance

D Direct method calls between classes

It decouples components, so they can work independently and be maintained easily.

When a publisher raises an event, what happens?

A Only the first subscriber is notified

B All subscribers attached to the event are notified

C No subscribers are notified automatically

D Subscribers must poll the publisher

All subscribers attached to the event are called automatically when the event is raised.

Explain how the Publisher-Subscriber model works in C# with an example of subscribing and raising an event.

Think about how events and delegates work together.

Describe the advantages of using the Publisher-Subscriber execution model in software design.

Consider how components communicate without tight connections.