EVENT DRIVEN COURSE

1. EDP
Introduction
K i t a w A .

2. Introduction
• Event-driven programming is a programming paradigm in
which the flow of the program is determined by events
• Event is an action or occurrence detected by a program;
and originates from mainly two sources:
• Users:
• mouse clicks, key presses
• Another programs:
• messages from other programs or threads
• Event-driven program is designed to react such events

3. Introduction
• In an event-driven application, there is generally a main
loop that listens for events, and triggers a callback
function when one of those events is detected
• A callback function, also called event handler, is a function
that is invoked when an event occurs
Initialization
Wait for events
Exit or
crash?
Call event
handler
Event
Handler
Stop
Start
Y N

4. Introduction
• Event-driven programming is the dominant paradigm used in
graphical user interfaces (GUIs)
• A user interface is a system by which people (users) interact
with the computer
• There are two main types of user interfaces:
• Text-Based User Interface or Command-Line Interface (CLI)
• Graphical User Interface (GUI)

5. Introduction
• Command Line Interface - CLI
• This is a text only interface, which only requires input from
the keyboard (usually referred to as “entering a command”)
• Typically, Enter key is pressed at the end of a command, after
which the computer will receive, parse and execute that
command
• The output of the command will be returned back to the
terminal as text lines
• This interface relies primarily on the keyboard

6. Introduction
• Command Line Interface - CLI
• The main advantages of a CLI are:
• users only need to utilize the keyboard and may need to
execute only few commands to complete the task
• a computer that is only using the command line takes a lot
less of the computers resources
• The main disadvantages of a CLI are:
• difficult for new users to learn
• relies heavily on recall rather than recognition
• navigation is often more difficult

7. Introduction
• Graphical User Interface - GUI
• It is a type of interface that allows users to communicate with
applications in the form of images/animations/icons as
opposed to text
• This interface presents the user with the information/actions
through graphical objects (i.e. GUI Controls or Widgets)
• Both mouse and keyboard can be used for the interaction
• The user performs actions by directly manipulating graphical
objects on the screen

8. Introduction
• Graphical User Interface - GUI
• The main advantages of a GUI are:
• less expert knowledge is required to use it (more user friendly)
• easier to navigate
• The main disadvantages of a GUI are:
• consumes system resources
• slower compared to CLI

9. What is .NET?
• .NET is a developer platform made up of tools, programming
languages, and libraries for building different types of
applications
• It is created by Microsoft
• Its applications are multi-platform applications
• It has been designed in such a way that it can be used from
any of the following languages: C#, C++, Visual Basic, etc
• It consists of an enormous library of codes used by the client
languages such as C# using object-oriented programming
(OOP) techniques

10. What is .NET?
Common Language Runtime
Framework Class Library
ADO.NET
WinForms
Common Language Specification, Common Type System
C#
ASP.NET WPF
Visual Basic C++
.NET
Framework

11. Common Language Runtime
• The CLR is responsible for maintaining the execution
of all applications developed using the .NET library
• It provides various services to managed code:
• Compilation and execution
• Integrating software components written in different .NET
languages,
• Garbage collection, and more.

12. Common Language Runtime
• Managed code is compiled into machine-specific
instructions in the following steps:
• First, the code is compiled into Microsoft Intermediate
Language (MSIL)
• When the app executes, another compiler (known as the
just-in-time compiler or JIT compiler) in the CLR translates
the MSIL in into machine-language code (for a particular
platform)
• The machine-language code executes on that platform

13. Common Language Runtime
• The Framework provides a high level of language
interoperability
• Because software components written in different .NET
languages (such as C# and Visual Basic) are all compiled into
MSIL, the components can be combined to create a single
unified program
• Thus, MSIL allows the .NET Framework to be language
independent

14. Framework Class Library
• The .NET framework class library is a library of classes and
interfaces that provide access to system functionality
• It is the foundation on which .NET Framework applications are
built
• The library is categorized into a number of namespaces
• The System.Windows namespaces contain types used in
Windows Presentation Foundation (WPF) applications,
• System.Windows.Forms and its child namespaces are used for
developing Windows Forms applications.

15. ADO.NET
• ADO.NET provides consistent access to data sources such as
SQL Server and XML
• Applications can use ADO.NET to connect to these data
sources and perform CRUD operations:
• Create,
• Read,
• Update and
• Delete data

16. System.Windows (WPF)
• System.Windows provides an object-oriented set of classes
that enable you to develop rich Windows applications
• With this module and some additional code you can:
• design UI
• read information from the user
• respond to the information provided
• manipulate data from external sources (i.e. files and
databases)

17. Common Type System
• The Common Type System (CTS) standardizes the data types
of all programming languages under the umbrella of .NET to a
common data type for easy and smooth communication
C# Visual Basic
System.Int32
Integer
int

18. Common Language Specification
• CLS is a set of basic language features that .NET Languages
needed to develop Applications and Services , which are
compatible with the .NET Framework.
• When there is a situation to communicate Objects written in
different .NET Complaint languages , those objects must
expose the features that are common to all the languages
• For example, one rule is that you cannot use multiple inheritance within
.NET Framework. As you may know C++ supports multiple inheritance
but; that’s not allowed to use such a C++ code within C# because it
doesn’t supports multiple inheritance
• Another rule is that you cannot have members with the same name but
different cases i.e. you cannot have add() and Add() methods. This easily
works in C# because it is case-sensitive but because VB is not case
sensitive, it’s not possible to use such a code

19. .NET Implementations
• Three implementations:
1. .NET Framework is the original implementation of .NET. It supports
running websites, services, desktop apps, and more on Windows
2. .NET Core is a cross-platform implementation for running websites,
services, and console apps on Windows, Linux, and macOS. This
implementation is open source on GitHub
3. Xamarin/Mono is a .NET implementation for running apps on all the
major mobile operating systems, including iOS and Android

20. EDP
END
T h a n k y o u !
Kitaw A.