Transcript CIS 451 E-Commerce Application Development

CIS 338: Client/Server
Application Development
with Visual Basic.NET
Dr. Ralph D. Westfall
April, 2011
What Can Computers Do?
Individual exercise:
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identify things that can't be done without
computers (impossible/impractical)?
How can computers do such things?
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capabilities of computers: examples of?
 doing same things better
 doing new things (couldn't do before)
Programming Languages
How many in the world?
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see The Language List
How many have multiple web pages
devoted to them?
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another list (180+ entries, but a fair
amount of overlap)
A "Perfect" Language?
Buzz group exercise:
Identify desirable features/advantages:
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for the student/learner, or for the
experienced programmer?
for amateurs (use once in a while), or for
professionals (use all the time)?
for organizations, businesses?
in general?
Visual Basic.NET in Context
When viewing the following slides, and
through the remainder of this course,
think about:
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what computers can do?
features/capabilities that programming
languages should have?
C/S with VB.NET Overview
What is client/server computing?
How does Visual Basic.NET relate to
client/server computing?
Introduction to Visual Basic.NET
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objects
integrated development environment
program code
advantages and disadvantages
Client/Server Computing
services – data, computations, etc.
server(s) – computer(s) that provides
services
client – computer that gets services
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messages to server(s) requesting services
advantage = efficiency
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clients & server(s) each what do best
Client/Server Advantages
relative to mainframe systems
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GUI (WIMP) easier for users to work with
flexible: easier to adapt to different
environments/different types of use
interoperability: easier to share data with
other applications
scalability: can work with limited activity,
or with larger volumes/high traffic
Client/Server Examples
web servers (Apache, IIS)
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lots of HTML, some audio, video, etc. files
send files over Internet when requested
handle login security
Email servers and email clients
PC clients
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show/play files on screen and speakers
encrypt data to send to server
Client/Server Examples - 2
database server
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fast access to large amounts of data
high-level validation
security
PC client
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data entry
 low-level validation
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showing reports created from server data
VB.NET and Client/Server
object oriented programming (OOP)
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built-in objects handle many of details
component assembly approach (like Lego)
VB.NET object for client user interface
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forms, menus, reports/printing
[demonstration of form/controls]
VB.NET objects for interacting with server
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database connection, records from database
Visual Basic.NET Code
modeled on the BASIC and Java languages
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Java and JavaScript look more like C/C++
BASIC stands for: beginners all-purpose
symbolic instruction code
control structures (different from Java, etc.)
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sequence (one instruction after another)
selection (if … then … else, select case …)
repetition (looping: for…next, do while…)
transfer of control (subroutines, functions)
Visual Basic.NET Code - 2
built-in functions
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e.g., CInt (convert to integer), CStr
(convert to string), Now (date/time),
Round (to integer or decimal values),
IsNumeric (tells if a value is a number)
numerous data types
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8 (!) integers, 3 decimals, Boolean, String,
character
compiled into MSIL code
Visual Basic.NET Code - 3
With … End With
Advantages of VB 6
works with Windows
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95% of OS (operating system) market
popular
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3 million VB developers in world (.NET?)
used by many larger organizations
easy to learn to write small applications
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creating forms, adding controls, writing
simple code
More Advantages of VB 6
high productivity
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does a lot of things for you automatically
suitable for rapid application
development
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prototyping "quick and dirty" sample
systems
developing complete systems
Rapid Application Development (RAD)
Even More Advantages of VB 6
can be a component of scalable, multiplatform systems
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VB front end to almost any
hardware/database platform
multi-tier architectures
works with the Internet
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compiled ActiveX controls work with IE
ASP.NET works with many browsers
Disadvantages of VB 6
different from, not “elegant” like Java,
C/C++ (VB.NET much better on this)
slower performance than C/C++
less features/power than C/C++, Java
less control over operating system and
other lower level computer activities
Microsoft support ended 2008
More Disadvantages of VB 6
too easy to learn?
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bad systems developed by inexperienced
developers
harder languages (C/C++, Java, VB.NET)
are more impressive to recruiters
Advantages of VB.NET
completely object oriented
.NET Framework makes code
interoperable with code written in other
languages
more powerful than VB 6
more esthetic? (looks like Java)
Visual Studio.NET is a very powerful
development tool
Disadvantages of VB.NET
harder to learn than VB 6
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syntax is more detailed
substantial differences from VB 6
not as easy to work with?
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if you turn error checking (Option Strict)
on, Visual Studio forces you to write code
according to the syntax requirements
but keeping error checking on helps you
develop code that is less likely to crash