Event-driven programming is a programming paradigm where the flow of a program is determined by events. There are two main sources of events - users and other programs. An event-driven program contains a main loop that listens for events and triggers callback functions when events are detected. Callback functions are event handlers that are invoked in response to events. Graphical user interfaces predominantly use the event-driven paradigm.

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.