Event-Driven programming is a programming paradigm where the program primarily responds to events - typically generated by a user, but also potentially from sensors, network connections, or other sources. We cover it here because event-driven programming is a staple of graphical user interfaces. These typically display a fairly static screen until the user interacts with the program in some meaningful way - moving or clicking the mouse, hitting a key, or the like.

As you might suspect, event-driven programming is often used alongside other programming paradigms, including structured programming and object-orientation. We’ll be exploring how event-driven programming is implemented in C# in this chapter, especially how it interacts with Windows Presentation Foundation.

Key Terms

  • Event
  • Message Loop
  • Message Queue
  • Event Handler
  • Event Listener
  • Event Arguments

C# Keywords and Operators

  • event
  • EventArgs
  • +=
  • -=
  • ?.

Key Skills

The key skills to learn in this chapter are how to write event listeners, attach event listeners to event handlers, and how to define custom event handlers.