Zahid Iqbal

یہ ایک تجرباتی تحریر ہے اردو کی۔

Admin — Mon, 17 Oct 2011 11:43:00 +0400

یہ ایک تجرباتی تحریر ہے اردو کی۔

ASP.Net MVC Hello World

zahid — Thu, 11 Aug 2011 21:42:00 +0400

In this blog, I will try to explain how to create a Hello World ASP.Net MVC application

Before developing ASP.Net MVC 2 Application you have care about Visual Studio requirements

Visual Studio 2010 any edition or
Free Visual Web Developer Express
- There is nothing more to do because these both already include ASP.Net MVC 2 by default
For Visual Studio 2008 you have to
- SP1 (any edition of VS 2008)
- Visual Web Developer 2008 with SP1
- Because these do not include ASP.Net MVC 2 by defaul so you need to install
- Install ASP.Net MVC 2, you can download from http://www.asp.net/mvc/

After fulfilling the requirements mentioned above, I suppose you are working in VS 2010

Now open VS 2010
Click on File
Click on Project
There will be two types of ASP.Net MVC projects templates
1. ASP.Net MVC 2 Web Application
2. ASP.Net MVC 2 Empty Web Application
I click on ASP.Net MVC 2 Empty Web Application
Name your application whatever you want I here put name MyFirstHelloWorld
Click Ok

You can see various structures here as shown in picture above. You can say in other words, MVC has created a road map for us. Using this road map or structure we can create our MVC application.

For adding Controller, you just need to right click on Controllers -> Add New Controller

For adding Models, right click on Models -> Add New Model

For adding Views, right click on Views -> Add New Views

Remember, in model, you can just add classes. It is just App_Code in simple ASP.Net

Now come to point

Right click Controller
Add -> Controller
Name it whatever your want
Click on Add button

You will see

It just create HelloWordController Class having Index() Action with returning object ActionResult and View().

Now if anyone calls HelloWorld from web browser, it first calls the HelloWorldController. It then calls Index () function. This Index function will return View() and this View() will be translated into ActionResult. In the lass this ActionResult will display information on the web browser.

Now add new Controller by click on Controller -> Add -> Controller
You can also add Controller by clicking on ActionResult

You can name whatever you want but here i left it same as it is now Click on Add

You can see in solution explorer, in Views it added Index.aspx web page here
Now come to Index.aspx web page,

Just for testing I wrote some thing...
Now press CRTL + F5
You will see output mentioned below

Oh My God, What happened, I did what as instructions mentioned then why this error flagged
Don't be panic
This is error because you have not yet invoked any kind of action
If you remember out action was HelloWorld and this HelloWorld will invoke Index.aspx web page
Now go to URL and pad right HelloWorld and see the result
Note: If you type index.aspx then it will flag error of HTTP404. I let this error to ender users to know why it is happened

Define XPATH?

zahid — Wed, 10 Aug 2011 21:11:00 +0400

It is an XML query language to select specific parts of an XML document. Using XPATH you can address or filter elements and text in a XML document. For instance a simple XPATH expression like “Invoice/Amount” states find “Amount” node which are children of “Invoice” node.

What is XSLT?

zahid — Wed, 10 Aug 2011 21:09:00 +0400

XSLT is a rule based language used to transform XML documents in to other file formats. XSLT are nothing but generic transformation rules which can be applied to transform XML document to HTML, CS, Rich text etc.

You can see in the above figure how the XSLT processor takes the XML file and applies the XSLT transformation to produce a different document.

What are the core functionalities in XML .NET framework? Can you explain in detail those functionalities?

zahid — Wed, 10 Aug 2011 21:08:00 +0400

The XML API for the .NET Framework comprises the following set of functionalities:

XML readers

With XML readers the client application get reference to instance of reader class. Reader class allows you to scroll forward through the contents like moving from node to node or element to element. You can compare it with the “SqlDataReader” object in ADO.NET which is forward only. In short XML reader allows you to browse through the XML document.

XML writers

Using XML writers you can store the XML contents to any other storage media. For instance you want to store the whole in memory XML to a physical file or any other media.

XML document classes

XML documents provides a in memory representation for the data in an XMLDOM structure as defined by W3C. It also supports browsing and editing of the document. So it gives you a complete memory tree structure representation of your XML document.

What is the main difference between MSML and .NET Framework XML classes?

zahid — Wed, 10 Aug 2011 21:07:00 +0400

MSXML supports XMLDOM and SAX parsers while .NET framework XML classes support XML DOM and XML readers and writers.

MSXML supports asynchronous loading and validation while parsing. For instance you can send synchronous and asynchronous calls to a remote URL. But as such there is not direct support of synchronous and asynchronous calls in .NET framework XML. But same can be achieved by using “System.Net” namespaces.

How was XML handled during COM times?

zahid — Wed, 10 Aug 2011 20:44:00 +0400

During COM it was done by using MSXML 4.0. So old languages like VB6, VC++ used MSXML 4.0 which was shipped with SP1( Service Pack 1).

A)In What scenarios will you use a DOM parser and SAX parser?

zahid — Wed, 10 Aug 2011 20:41:00 +0400

If you do not need all the data from the XML file then SAX approach is much preferred than DOM as DOM can quiet memory intensive. In short if you need large portion of the XML document its better to have DOM.
With SAX parser you have to write more code than DOM.
If you want to write the XML in to a file DOM is the efficient way to do it.
Some time you only need to validate the XML structure and do not want to retrieve any Data for those instances SAX is the right approach

What are the standard ways of parsing XML document? What is a XML parser?

zahid — Wed, 10 Aug 2011 20:26:00 +0400

XML parser sits in between the XML document and the application who want to use the XML document. Parser exposes set of well defined interfaces which can be used by the application for adding, modifying and deleting the XML document contents. Now whatever interfaces XML parser exposes should be standard or else that would lead to different vendors preparing there own custom way of interacting with XML document.

There are two standard specifications which are very common and should be followed by a XML parser:-

DOM: - Document Object Model.

DOM is a W3C recommended way for treating XML documents. In DOM we load entire XML document into memory and allows us to manipulate the structure and data of XML document.

SAX: - Simple API for XML

SAX is event driven way for processing XML documents. In DOM we load the whole XML document in to memory and then application manipulates the XML document. But this is not always the best way to process large XML documents which have huge data elements. For instance you only want one element from the whole XML document or you only want to see if the XML is proper which means loading the whole XML in memory will be quiet resource intensive. SAX parsers parse the XML document sequentially and emit events like start and end of the document, elements, text content etc. So applications who are interested in processing these events can register implementations of callback interfaces. SAX parser then only sends those event messages which the application has demanded.

Above is a pictorial representation of how DOM parser works. Application queries the DOM Parser for “quantity” field. DOM parser loads the complete XML file in to memory.

DOM parser then picks up the “quantity” tag from the memory loaded XML file and returns back to the application.

SAX parser does not load the whole DOM in to memory but has event based approach. SAX parser while parsing the XML file emits events. For example in the above figure its has emitted Invoice tag start event, Amount Tag event, Quantity tag event and Invoice end tag event. But our application software is only interested in quantity value. So the application has to register to the SAX parser saying that he is only interested in quantity field and not any other field or element of the XML document. Depending on what interest the application software has SAX parser only sends those events to the application the rest of events is suppressed. For instance in the above figure only quantity tag event is sent to the application software and the rest of the events are suppressed.

Which are the namespaces in .NET used for XML?

zahid — Wed, 10 Aug 2011 20:25:00 +0400

“System.xml.dll” is the actual physical file which has all XML implementation. Below are the commonly used namespaces:-

System.Xml
System.Xml.Schema
System.Xml.XPath
System.Xml.Xsl