OOP Class9

Anatomy of an aspx page

Page Directive The page directive must be on the first line of an aspx page. It consists of Name/Value Pairs and sets parameters that will be used throughout the execution of the page ie. the language.

<%@ Page language="c#" debug="True" trace="False"%>

C# Code may be embedded in the page using script tags similar to javascript

<script language="c#" runat="server"> </script>

Notice the runat attribute is set to 'server'. This is what makes the code execute on the server rather than be parsed by the client.

Console applications start executing in the main method

<csharp>public static void Main() {}</csharp>

The .Net Framework can also execute on the web. Rather than having a Main method a web page starts it's execution with a method called Page_Load

<csharp>public Page_Load { }</csharp>

There are actually several method that are executed in an aspx page.

http://samples.gotdotnet.com/quickstart/aspplus/

Simple Aspx Page

http://iam.colum.edu/oop/classsource/class8/Aspx/hello.aspx hello.aspx

http://iam.colum.edu/oop/classsource/class8/Aspx/hello2.aspx hello2.aspx

http://iam.colum.edu/oop/classsource/class8/Aspx/Label.aspx Label.aspx

In class
Build three hello aspx pages similar to the ones above

Dogs on the web

DogWeb

HTML and HTTP

Http is a stateless protocol. There is mo mechanism built in to the protocol that allows the server to remeber clients or requests. An http simply responds to http verbs GET, POST, PUT, DEL, TRACE etc. contained in RFC 2068 HTTP/1.1

regular html forms post information using forms in 2 ways with a get or a post http request.

Get

Get send information to the server using the URI. Limited to 1024 character in some browsers and servers.

Example http://iam.colum.edu/oop/classsource/class9/simpleGet.html simpleGet.html - source

The simpleGet.html pages form has the action of 'simpleGet.aspx' this mean that when the form is submitted the browser will request the 'simpleGet.aspx' with whatever parameters are in the form. Since the method = get these pararmeters will show up are query string parameters

URI and querystring parameters

URI - Universal Resource Identifier http://src.doc.ic.ac.uk/computing/internet/rfc/rfc1630.txt RFC1630

Http URI

Protcol	Host	Port	Path	File	Fragment identifier	Querystring
http://	info.cern.ch	:8000	/imaginary/test/	file.html	#link	?test=yes

Post

Post posts the variables in the HTTP Header.

Example http://iam.colum.edu/oop/classsource/class9/simplePost.html simplePost.html - source

FirstName:
LastName:
Header Name 	Value HttpMethod 	GET
Connection 	keep-alive
Keep-Alive 	300
Accept 	text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Charset 	ISO-8859-1,utf-8;q=0.7,*;q=0.7
Accept-Encoding 	gzip,deflate
Accept-Language 	en-us,en;q=0.5
Cookie 	ASP.NET_SessionId=ezfgw255ix0zd5yogj3eawej
Host 	imdev
Referer 	http://imdev/infod/jeff/
User-Agent 	Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.1) Gecko/20060111 Firefox/1.5.0.1

REST

Representational state transfer

https://www.ibm.com/developerworks/webservices/library/ws-restful/

http://www.infoq.com/articles/rest-introduction

http://iam.colum.edu/oop/classsource/class9/htmlForms.html htmlForms.html - source

Courses on the Web

Student Web

Response Object

Response.Write()

http://iam.colum.edu/oop/classsource/class10/Response/Response1.aspx Response1.aspx - source

Response.End()

http://iam.colum.edu/oop/classsource/class10/Response/Response2.aspx Response2.aspx - source

Response.Clear()

http://iam.colum.edu/oop/classsource/class10/Response/ResponseClear.aspx ResponseClear.aspx - source

Response.Flush()

http://iam.colum.edu/oop/classsource/class10/Response/ResponseFlush.aspx ResponseFlush.aspx - source

Debugging with response object

Using the response buffer can be extreemely usefull for debugging. Sometime you may have to setup a small debug system to help catch errors in object that do not inherit from System.UI.Page.

Response.Flush()

http://iam.colum.edu/oop/classsource/class10/Response/ResponseDebug.aspx ResponseDebug.aspx - source

Home Work

Convert one of your classes to work as an aspx page.

Have a nice break....

Interfaces

Interfaces - implements or derives from

An interface is a class that lacks implementation. The only thing it contains are definitions of events, indexers, methods and/or properties. The reason interfaces only provide definitions is because they are inherited by classes and structs, which must provide an implementation for each interface member defined. Since classes in c# can only be derived from one other class ( in c++ it is possible to derive from many) interfaces are used for multiple inheritance. Like abstract classes you cannot create an instance of an interface on derive from it.

You cannot create an instance of an interface.

Interfaces cannot contain any implementation.

Interfaces are basically a contract between classes. When a class implements an interface it is promising to implement the propery and method signature of that interface. This helps with abstraction and encurages polymorphism.

In order to specify that a class implements an inteface you use a : after the class name:

<csharp>public class NewDog : IWalkable</csharp>

This means that the NewDog class implements the IWalkable interface.

Interfaces support multple inheritance.

<csharp>public class NewDog : IWalkable,IBark</csharp>

Now the NewDog Class promises to implement the IWalkable and the I Bark interface.

Phone interface example with single inhertance

phoneIFace.cs -source

Multiple interface inheritance - inherits IPhone, Cell, POTS phoneIFacePOTS.cs -source

Phone Interface UML

IComparable and Polymorphism

In order to allow build in Arry type like the ArrayList to be able to Sort and Reverse your classes need to implement the IComparable Interface. System.IComparable on MSDN

After your classes implement this interface it will allow for polymorphic method like Sort and Reverse to work.

Here is an exmaple of a dog array that will not sort

dogSimple.cs

This IComplare Interface has calls for a methpod called CompareTo. The CompareTo method shoudl retun an positive integerg if that the current object is grater that the object that is being compared. It should oreturn 0 is they are equal. And it should return a negative integer is the current object is less than the compared object.

The UML for IComparable

The UML for a dog that implemets IComparable

Now here is an example of a Dog class that implements the IComparable inteface.

dogICompare.cs

Other Resources on Interfaces

ArsDigita University Course 04: Object-oriented Program Design and Software Engineering - Lecture Notes 4

ArsDigita University Course 04: Object-oriented Program Design and Software Engineering - Lecture Notes 5

Web Forms

Examples of Web Forms

http://iam.colum.edu/oop/classsource/class9/aspForms.aspx aspForms.aspx - Source

todo examples of all the html elements and how they react to form submits

Persisting Data

POST and GET

an asps page posting to itself

Events in c# on the web

Event handlers

OnClick

http://iam.colum.edu/oop/classsource/class9/events/events1.aspx events1.aspx - source

OnCommand

http://iam.colum.edu/oop/classsource/class9/events/events2.aspx events2.aspx - source

http://iam.colum.edu/oop/classsource/class9/events/events3.aspx events3.aspx - source

Home Work

Make an post an catch aspx page with a form of your very own that asks questions about one of your objects. Use regular html form and aspx events to demostrate you class.

Use the form values to create a new instance of your class.

Get and read Intro and Chapter 1 of Head Start Design Patterns