Introduction to visual programming C#

Learning Outcomes In this chapter, you will learn about :  Event-Based Programming  The Event Based Model  Application Programming Interface (API)  Different types of programs  The first program with visual C#

Event Based Programming  Event-based programs provide fully functioning GUIs  An event is initiated by a user action  A program must: – Correctly assess which specific event has occurred – Provide the appropriate code to perform an action based on the identified event

Event Based Programming

 Actions that trigger events include: –Placing the mouse pointer over a button and clicking the left mouse button –Using the TAB key until the desired button is highlighted with a dotted line then pushing the Enter key –Pressing an accelerator key  The sequence of events in a program are controlled by the user

 Operating system: –Has total control of computer –Never relinquishes control to any executing programs  Most executing programs spend the majority of their time in a sleep type of mode  When an event occurs: –The operating system passes event information to the appropriate application –Permits the application to take action The Event-Based Model

Visual Studio.Net controls designer Properties, events

GUI Tree Structure Panel Button Form Label GUIInternal structure containers Panel Button Form Label

Components API Properties Like member fields Get, set E.g. Button1.Text = “Press Me” Methods Like member functions Tell component to do something E.g. Button1.Show( ) Events Like callback functions Receive notifications from component E.g. Button1.Click(e)

Non-interactive Linear execution program: main() { code; } Typical command line program

Interactive command line program  User input commands  Non-linear execution  Unpredictable order program: main() { decl data storage; initialization code; loop { get command; switch(command) { command1: code; command2: code; … }

 User input commands  Non-linear execution  Unpredictable order  Event callback procs Typical GUI program GUI program: main() { decl data storage; initialization code; create GUI; register callbacks; main event loop; } Callback1()//button1 press {code; } Callback2()//button2 press {code; } …

C Sharp (C#)  C# was designed specifically for the.NET platform as a language that would enable programmers to migrate easily to.NET.  C# is object oriented and has access to a powerful class library of prebuilt components.  It has roots in C, C++ and Java, adapting the best features of each.  Microsoft introduced C# along with its.NET strategy in  The.NET platform allows applications to be distributed to a variety of devices.

The first program

The purpose of the code is so that you can add your own methods to handle the logic for your application, such as what happens when the user clicks the OK button The first program

Double click the ok Button on the form. A new method has been added called ok_click. We add the code to the ok_click method The first The first program