1. Programming the Web Using Visual Studio .NET

2. Introduction VS.NET permits programming in a visual environment
That means developing via forms using drag-and-drop techniques
Hand-coding is available also
We’ll be using Visual Basic.NET

3. Object-Oriented Concepts
Object-oriented programming
Certain block of code treated as reusable objects
Accept certain inputs
Produce certain outputs
Keep track of certain data (values)
Programmer doesn’t have to know how the output is produced, only how to manipulate the object
Programmer has to know what parts of an object can be manipulated by what means

4. Object-Oriented Concepts
Properties
Contain values
Addressable
That is, programmer has access to the property
Access can be restricted
Local access only
Controlled
“Friendly” access
A known caller
Global access
No control – any program can access

5. Object-Oriented Concepts
Methods
Functions that the object can perform
Can supply data via arguments
Can return a value
Don’t have to know how they work
Do have to know:
What do you give it (parameters)
What do you get back (return value)
What it changes (properties)
It is a way to safely access or change properties
e.g. a method could accept a request for a withdrawal from an ATM
Validate the amount is between $10 and $400 before issuing the money and updating accounts

6. Object-Oriented Concepts
Events
Triggers that are activated in specific situations
Affects object without user intervention
Many objects are already part of the VS.NET environment
You don’t have to create them, only use them
You can build your own objects if you need to

7. Object-Oriented Concepts
Objects are derived from classes
Classes are basically templates
Car is a class
4 wheels
Engine
An object is an instance of a class
Creating an object is called instantiation
Making a Honda is instantiating a car
VIN JHMEJ854*WC is a specific car

8. Object-Oriented Concepts
Encapsulation
Objects can be used without knowing what goes on inside them
Inheritance
New classes can be created based on base classes
Each new derived class
Inherits the properties and methods of the base class
May have properties and methods not in the base class

9. Object-Oriented Concepts
Polymorphism
Properties and methods of both base and derived classes can have the same name and be used in the same way
- or -
Definitions can do different “tasks” depending on the type of data worked with
This means that the output of a method may be produced by completely different internal processing methods (using the same “name”)
The user doesn’t care
You’ve used a type of polymorphism in JavaScript
+ operator
In a math context it adds the numbers
In a string context it concatenates the strings

10. .NET Structures & Languages
Common Language Runtime (CLR)
CLR is an intermediate state
Not source
Not object
Makes VS.NET applications machine independent
Code running within the CLR is called managed code
Allows VB, C++, C# code to easily co-exist

11. .NET Structures & Languages
Communications protocols
VS.NET supports many
TCP/IP is the most common
HTTP
FTP
Necessary for networked environment
Multiple computers
Multiple operating systems
Encoding formats
ISO
Unicode

12. .NET Structures & Languages
VS.NET supports
Visual Basic (VB.NET) C#
J# (discontinued)
C++
Others being added
We’ll be using VB.NET
It’s components are …

13. .NET Structures & Languages
Variables
Strongly typed
Name begins with alphabetic character
May contain alphabetic characters or digits
No special characters or punctuation symbols
No more than 255 characters in length
Cannot match a reserved word
Declaration examples:
Dim SSN as String
Dim salesTax, interest as Double
Dim age as Integer

14. .NET Structures & Languages
Constants
Literals (simply a value): Const 19.95
Symbolic (includes name): Const TVPrice=19.95
Comments
Begins with apostrophe

15. .NET Structures & Languages
Data types
Boolean
Byte
Char
Date
Double
Integer
Long
Object
Single
String
User-defined

16. .NET Structures & Languages
Operators
Assignment =
Arithmetic
+ - / * ^
Relational
< <= = <> >= >
Like
Wild cards * ?

17. .NET Structures & Languages
Operators (cont.)
Logical
and or
Concatenation +
&
Concat
Result = String.Concat(Str1, Str2)

18. .NET Structures & Languages
Control Structures
If…Then…Else…End If
Note: {} not needed
Select…Case
Do While…Loop
Do…Loop While|Until…
While…End While
For…To…Next

19. Example Application
What savings are needed to achieve a specific retirement goal?
Variables
Amount desired at retirement
Amount saved each month
Time until retirement
Interest rate

20. Example Application Web page format (client or user side)
Welcome page with link to a form
Data entry form
Results shown in browser window
Could be update of current page
Could be a new page
Validation of input on client side
JavaScript
Ensure numbers are numbers
Ensure data is within a valid range
Etc.
Processing on server side
Computations (usually intensive)
Retrieval of sensitive data
Preparation of presentation of data

21. Example Application Server-side processing is a little different
Web form
Web page in HTML
Contains a form: <form>…
Form “written” in HTML on client side
Sent to the client from the server
Page & form start on server
Contains HTML and other elements (XML)
Application also includes code behind the page
Web form and Code-Behind page automatically generated by VS.NET