1. Event Driven Programming
Key Features

2. Event Driven Programs
 Typically used for most modern day
software applications examples include:
word processing, spreadsheets, drawing
packages etc.
 Usually used for GUIs where many types
of events are generated i.e. clicking on a
button or another object

3. Key features
 Event Handlers
 Trigger Functions
 Events
 Event Loops
 Forms
 Flexibility
 Service oriented
 Suitability for GUIs
 Simplicity of programming
 Time Driven

4. Event Handlers
 VB.Net uses subroutines for event
handling, with the name of the object
followed by the name of the event – see
below: Event
Event
Handler

5.  ByVal means it is passing the variable by value.
 sender is an object of type System.Object. All objects in .NET
inheirit from System.Object, as such it is passing the control that is
causing the event to fire.
 e is an object of type System.EventArgs where EventArgs is the
Class for event arguments or, the arguments the event is passed.
 It contains information you need to process the event. The
information available depends on the type of event that was raised.
Since the members available through the "e" argument depend on
the kind of action that raised the event, it is important to use an
event that provides the information you're interested in.

7. Trigger functions
 These are used along with the object’s name to determine with event handler to run
 Every object has a range of trigger functions, one for each possible event that can
happen to it. For example, txtText could have an event handler for the following
triggers: GotFocus, TextChanged etc...
 Temporal triggers mean triggers set off by duration of time
 State triggers are when the current situation causes a certain set of procedures to run
 What is the trigger here??

8. Event Loops
 Event Driven Programs have event loops built into the
environment. The loops keep testing the interface to
detect whether anything has happened, such as clicking
on a button or typing into a textbox etc.
 Event Loops are also known as event listeners

9. Flexibility
 Programmers have erroneous control over
where to place code and how to start it.
 Every object has a good choice of events
that a program can respond to. These
events give an excellent level of control
over exactly what the program will
respond to when the user does something