Lokesh sharma

asp.net interview questions and answers

2011-09-16T00:42:00.001-07:00

When was .NET announced?

Bill Gates delivered a keynote at Forum 2000, held June 22, 2000, outlining the.NET 'vision'. The July 2000 PDC had a number of sessions on .NET technology,and delegates were given CDs containing a pre-release version of the .NETframework/SDK and Visual Studio.NET.

When was the first version of .NET released?

The final version of the 1.0 SDK and runtime was made publicly available around6pm PST on 15-Jan-2002. At the same time, the final version of VisualStudio.NET was made available to MSDN subscribers.

What platforms does the .NET Framework run on?

The runtime supports Windows XP, Windows 2000, NT4 SP6a and Windows ME/98.Windows 95 is not supported. Some parts of the framework do not work on allplatforms - for example, ASP.NET is only supported on Windows XP and Windows2000. Windows 98/ME cannot be used for development.
IIS is not supported on Windows XP Home Edition, and so cannot be used to hostASP.NET. However, the ASP.NET Web Matrix
web server does run on XP Home.
The Mono project is attempting to implement the .NET framework on Linux.

What is the CLR?

CLR = Common Language Runtime. The CLR is a set of standard resources that (intheory) any .NET program can take advantage of, regardless of programminglanguage. Robert Schmidt (Microsoft) lists the following CLR resources in hisMSDN PDC# article:
Object-oriented programming model (inheritance, polymorphism, exceptionhandling, garbage collection)
Security model
Type system
All .NET base classes
Many .NET framework classes
Development, debugging, and profiling tools
Execution and code management
IL-to-native translators and optimizers
What this means is that in the .NET world, different programming languages willbe more equal in capability than they have ever been before, although clearlynot all languages will support all CLR services.

What is the CTS?

CTS = Common Type System. This is the range of types that the .NET runtimeunderstands, and therefore that .NET applications can use. However note thatnot all .NET languages will support all the types in the CTS. The CTS is asuperset of the CLS.

What is the CLS?

CLS = Common Language Specification. This is a subset of the CTS which all .NETlanguages are expected to support. The idea is that any program which usesCLS-compliant types can interoperate with any .NET program written in anylanguage.
In theory this allows very tight interop between different .NET languages - forexample allowing a C# class to inherit from a VB class.

What is IL?

IL = Intermediate Language. Also known as MSIL (Microsoft IntermediateLanguage) or CIL (Common Intermediate Language). All .NET source code (of anylanguage) is compiled to IL. The IL is then converted to machine code at thepoint where the software is installed, or at run-time by a Just-In-Time (JIT)compiler.

What does 'managed' mean in the .NET context?

The term 'managed' is the cause of much confusion. It is used in various placeswithin .NET, meaning slightly different things.Managed code: The .NET frameworkprovides several core run-time services to the programs that run within it -for example
exception handling and security. For these services to work, the code mustprovide a minimum level of information to the runtime.
Such code is called managed code. All C# and Visual Basic.NET code is managedby default. VS7 C++ code is not managed by default, but the compiler canproduce managed code by specifying a command-line switch (/com+).

Managed data: This is data that is allocated and de-allocated bythe .NET runtime's garbage collector. C# and VB.NET data is always managed. VS7C++ data is unmanaged by default, even when using the /com+ switch, but it canbe marked as managed using the __gc keyword.

Managed classes: This is usually referred to in the context ofManaged Extensions (ME) for C++. When using ME C++, a class can be marked withthe __gc keyword. As the name suggests, this means that the memory forinstances of the class is managed by the garbage collector, but it also meansmore than that. The class becomes a fully paid-up member of the .NET communitywith the benefits and restrictions that brings. An example of a benefit isproper interop with classes written in other languages - for example, a managedC++ class can inherit from a VB class. An example of a restriction is that amanaged class can only inherit from one base class.

What is reflection?

All .NET compilers produce metadata about the types defined in the modules theyproduce. This metadata is packaged along with the module (modules in turn arepackaged together in assemblies), and can be accessed by a mechanism calledreflection. The System.Reflection namespace contains classes that can be usedto interrogate the types for a module/assembly.
Using reflection to access .NET metadata is very similar to usingITypeLib/ITypeInfo to access type library data in COM, and it is used forsimilar purposes - e.g. determining data type sizes for marshaling data acrosscontext/process/machine boundaries.
Reflection can also be used to dynamically invoke methods (seeSystem.Type.InvokeMember ) , or even create types dynamically at run-time(see System.Reflection.Emit.TypeBuilder).

What is the difference between Finalize and Dispose (Garbage collection) ?
Class instances often encapsulate control over resources that are not managedby the runtime, such as window handles (HWND), database connections, and so on.Therefore, you should provide both an explicit and an implicit way to freethose resources. Provide implicit control by implementing the protected FinalizeMethod on an object (destructor syntax in C# and the Managed Extensions forC++). The garbage collector calls this method at some point after there are nolonger any valid references to the object. In some cases, you might want toprovide programmers using an object with the ability to explicitly releasethese external resources before the garbage collector frees the object. If anexternal resource is scarce or expensive, better performance can be achieved ifthe programmer explicitly releases resources when they are no longer beingused. To provide explicit control, implement the Dispose method provided by theIDisposable Interface. The consumer of the object should call this method whenit is done using the object.
Dispose can be called even if other references to the object are alive. Notethat even when you provide explicit control by way of Dispose, you shouldprovide implicit cleanup using the Finalize method. Finalize provides a backupto prevent resources from
permanently leaking if the programmer fails to call Dispose.

What is Partial Assembly References?

Full Assembly reference: A full assembly reference includes the assembly's textname, version, culture, and public key token (if the assembly has a strongname). A full assembly reference is required if you reference any assembly thatis part of the common
language runtime or any assembly located in the global assembly cache.

Partial Assembly reference: We can dynamically reference an assembly byproviding only partial information, such as specifying only the assembly name.When you specify a partial assembly reference, the runtime looks for theassembly only in the application
directory.
We can make partial references to an assembly in your code one of the followingways:
-> Use a method such as System.Reflection.Assembly.Load and specify only apartial reference. The runtime checks for the assembly in the applicationdirectory.
-> Use the System.Reflection.Assembly.LoadWithPartialName method and specifyonly a partial reference. The runtime checks for the assembly in theapplication directory and in the global assembly cache

Changes to which portion of version number indicates an incompatible change?
Major or minor. Changes to the major or minor portion of the version numberindicate an incompatible change. Under this convention then, version 2.0.0.0would be considered incompatible with version 1.0.0.0. Examples of anincompatible change would be a change to the types of some method parameters orthe removal of a type or method altogether. Build. The Build number istypically used to distinguish between daily builds or smaller compatiblereleases. Revision. Changes to the revision number are typically reserved foran incremental build needed to fix a particular bug. You'll sometimes hear thisreferred to as the "emergency bug fix" number in that the revision iswhat is often changed when a fix to a specific bug is shipped to a customer.

What is side-by-side execution? Can two application one using private assemblyand other using Shared assembly be stated as a side-by-side executables?

Side-by-side execution is the ability to run multiple versions of anapplication or component on the same computer. You can have multiple versionsof the common language runtime, and multiple versions of applications andcomponents that use a version of the runtime, on the same computer at the sametime. Since versioning is only applied to shared assemblies, and not to privateassemblies, two application one using private assembly and one using sharedassembly cannot be stated as side-by-side
executables.

Why string are called Immutable data Type ?
The memory representation of string is an Array of Characters, So onre-assigning the new array of Char is formed & the start address is changed. Thus keeping the Old string in Memory for Garbage Collector to be disposed.

What does assert() method do?

In debug compilation, assert takes in a Boolean condition as a parameter, andshows the error dialog if the condition is false. The program proceeds withoutany interruption if the condition is true.

What's the difference between the Debug class and Trace class?

Documentation looks the same. Use Debug class for debug builds, use Traceclass for both debug and release builds.

Why are there five tracing levels in System.Diagnostics.TraceSwitcher?

The tracing dumps can be quite verbose. For applications that areconstantly running you run the risk of overloading the machine and the harddrive. Five levels range from None to Verbose, allowing you to fine-tunethe tracing activities.

Web Services Interview Questions and answers

2011-09-16T00:40:00.001-07:00

What is SOAP?

Simple ObjectAccess Protocol (SOAP) is a lightweight protocol for exchange of information ina decentralized, distributed environment. It's an industry-standard messageformat that enables message-based communications for Web services.

2. What is UDDI?

UniversalDiscovery Description and Integration is like the "Yellow Pages" ofWeb services. A UDDI directory entry is an XML file that describes a businessand the services it offers. There are three parts to an entry in the UDDIdirectory. The "white pages" describe the company offering theservice, like, name, address, contacts, etc. The "yellow pages"include industrial categories based on standard taxonomies the StandardIndustrial Classification. The "green pages" describe the interfaceto the service in enough detail for someone to write an application to use theWeb service.

3. What is WSDL?

Web ServiceDescription Language (WSDL) defines an XML grammar for describing web services.This description includes details such as where to find the web service (itsURL), what methods and properties that service supports, the data types and theprotocols used to communicate with the service.

4. Describe Web Service (XML Web Service)?

A Web Service (XMLWeb Service) is a unit of code that can be activated using HTTP requests.Stated another way, a Web Service is an application component that can beremotely callable using standard Internet Protocols such as HTTP and XML. Amajor advantage of the Web services architecture is, it allows programs writtenin different languages on different platforms to communicate with each other ina standards-based way. Simply said, a Web service is a software service exposedon the Web through SOAP, described with a WSDL file and registered in UDDI.

5. Give examples of a WebService?

o Information sources like stock quotes, weather forecasts,sports scores etc that could easily incorporate into applications

o Services that provide commonly needed functionality forother services. Example, user authentication, usage billing etc

o Services that integrate a business system with otherpartners

6. What is SOAP Protocol message contains?

A SOAP Protocolmessage contains four parts:

· An envelope

· Encoding Rules

· RPC representation(Convention)

· Protocol binding(optional)

an envelop that defines a framework for describing what is in a message and howto process it, a set of encoding rules for expressing instances ofapplication-defined data types and a convention for representing remote procedurecalls (RPC). In protocol binding, almost all SOAP implementationssupport it as it's the only standardized protocol for SOAP. The HTTP binding isoptional.

Howmany types of diagrams are there in UML ?

There arenine types of diagrams in UML :-
Use case diagram: Theydescribe "WHAT" of a system rather than "HOW" the systemdoes it.They are used to identify the primary elements and processes that formthe system. The primary elements are termed as "actors" and theprocesses are called "use cases". Use Case diagrams shows"actors" and there "roles".
Class diagram:From the use case diagram we can now go to detail design of system, for whichthe primary step is class diagram. The best way to identify classes is toconsider all "NOUNS" in use cases as classes, "VERBS" asmethods of classes, relation between actors can then be used to define relationbetween classes. The relationship or association between the classes can beeither an "is-a" or "has-a" relationship which can easilybe identified from use cases.
Object diagram:An object is an instance of a class. Object diagram captures the state ofclasses in the system and their relationships or associations at a specificpoint of time.
State diagram:A state diagram, as the name suggests, represents the different states thatobjects in the system undergo during their life cycle. Object change inresponse to certain simulation so this simulation effect is captured in statediagram. So basically it has a initial state and final state and events thathappen in between them. Whenever you think that some simulations arecomplicated you can go for this diagram.
Sequence diagram: Sequencediagrams can be used to explore the logic of a complex operation, function, orprocedure. They are called sequence diagrams because sequential nature is shownvia ordering of messages. First message starts at the top and the last messageends at bottom. The important aspect of a sequence diagram is that it is time-ordered.This means that the exact sequence of the interactions between the objects isrepresented step by step. Different objects in the sequence diagram interactwith each other by passing "messages".
Collaboration diagram:A collaboration diagram groups together the interactions between differentobjects to fulfill a common purpose.
Activity diagram: Activitydiagram is typically used for business process modeling, for modeling the logiccaptured by a single use case, or for visualizing the detailed logic of abusiness rule.Complicated process flows in the system are captured in theactivity diagram. Similar to a state diagram, an activity diagram also consistsof activities, actions, transitions, initial and final states, and guardconditions. But difference is state diagrams are in context of simulation whileactivity gives detail view of business logic.
Deployment diagram:Deployment diagrams show the hardware for your system, the software that isinstalled on that hardware, and the middleware used to connect the disparatemachines to one another. It shows how the hardware and software work togetherto run a system. In one line its shows the deployment view of the system.
Component diagram: Thecomponent diagram represents the high-level parts that make up the system. From.NET angle point of view they form the "NAMESPACES". This diagramdepicts, at a3 1 4 high level, what components form part of the system and howthey are interrelated. Its shows the logical grouping of classes or group of othercomponents.

What is UML?

TheUnified Modeling Language (UML) is a graphical language for visualizing,specifying, constructing, and documenting the artifacts of a software-intensivesystem.UML provides blue prints for business process, System function,programming language statements, database schemas and reusable components.

B)Whichattribute is used in order that the method can be used as WebService ?

WebMethodattribute has to be specified in order that the method and property can betreated as WebService.

Whatthe different phase/steps of acquiring a proxy object in Webservice ?

Thefollowing are the different steps needed to get a proxy object of a webserviceat the client side :-
√ Client communicates to UDI node for WebService either through browser orUDDI's public web service.
√ UDII responds with a list of webservice.
√ Every service listed by webservice has a URI pointing to DISCO or WSDLdocument.
√ After parsing the DISCO document, we follow the URI for the WSDL documentrelated to the webservice which we need.
√ Client then parses the WSDL document and builds a proxy object which cancommunicate with Webservice.

Whichattribute is used in order that the method can be used as WebService ?

WebMethodattribute has to be specified in order that the method and property can betreated as WebService.

Whatis file extension of Webservices ?

.ASMX isextension for Webservices.

Whatthe different phase/steps of acquiring a proxy object in Webservice?

Thefollowing are the different steps needed to get a proxy object of a webserviceat the
client side :-

√ Client communicates to UDI node for WebService either through browser or
UDDI's public web service.

√ UDII responds with a list of webservice.

√ Every service listed by webservice has a URI pointing to DISCO or WSDLdocument.

√ After parsing the DISCO document, we follow the URI for the WSDL documentrelated to the webservice which we need.

√ Client then parses the WSDL document and builds a proxy object which cancommunicate with Webservice.

Whatis ObjRef object in remoting ?

AllMarshal() methods return ObjRef object.The ObjRef is serializable because itimplements the interface ISerializable, and can be marshaled by value. TheObjRef knows about :-

√ location of the remote object
√ host name
√ port number
√ object name.

Whatis marshalling and what are different kinds of marshalling ?

Marshalingis used when an object is converted so that it can be sent across the networkor across application domains.Unmarshaling creates an object from the marshaleddata.There are two ways to do marshalling :-

√ Marshal-by-value (MBV) :- In this the object is serialized into the channel,and a copy of the object is created on the other side of the network. Theobject to marshal is stored into a stream, and the stream is used to build acopy of the object on the other side with the unmarshalling sequence.

√ Marshaling-by-reference (MBR):- Here it creates a proxy on the client that isused to communicate with the remote object. The marshaling sequence of a remoteobject creates an ObjRef instance that itself can be serialized across thenetwork.

Objects that are derived from “MarshalByRefObject” are always marshaled byreference.All our previous samples have classes inherited from“MarshalByRefObject”

To marshal a remote object the static method RemotingServices.Marshal() isused.

RemotingServices.Marshal() has following overloaded versions:-

public static ObjRef Marshal(MarshalByRefObject obj)
public static ObjRef Marshal(MarshalByRefObject obj, string objUri)
public static ObjRef Marshal(MarshalByRefObject obj, string objUri,TyperequestedType)

The first argument obj specifies the object to marshal. The objUri is the paththat is stored within the marshaled object reference; it can be used to accessthe remote object.

The requestedType can be used to pass a different type of the object to theobject reference.
This is useful if the client using the remote object shouldn't use the objectclass but an
interface that the remote object class implements instead. In this scenario theinterface is the requestedType that should be used for marshaling.

Whatis Asynchronous One-Way Calls ?

One-waycalls are a different from asynchronous calls from execution angle that the.NET
Framework does not guarantee their execution. In addition, the methods used inthis kind
of call cannot have return values or out parameters.One-way calls are definedby using
[OneWay()] attribute in class.

W3School

Introductionto Web Services

WebServices can make your applications Web applications.

WebServices are published, found and used through the Web.

What YouShould Already Know

Before youcontinue you should have a basic understanding of the following:

HTML
XML

If youwant to study these subjects first, find the tutorials on our Home page.

What areWeb Services?

Web services are application components
Web services communicate using open protocols
Web services are self-contained and self-describing
Web services can be discovered using UDDI
Web services can be used by other applications
XML is the basis for Web services

How Doesit Work?

Thebasic Web services platform is XML + HTTP.
The HTTPprotocol is the most used Internet protocol.
XMLprovides a language which can be used between different platforms andprogramming languages and still express complex messages and functions.
Webservices platform elements

SOAP (Simple Object Access Protocol)
UDDI (Universal Description, Discovery and Integration)
WSDL (Web Services Description Language)

We willexplain these topics later in the tutorial

TheFuture of Web services

Don'texpect too much, too soon.
The WebServices platform is a simple, interoperable, messaging framework. It stillmisses many important features like security and routing. But, these pieceswill come once SOAP becomes more advanced.
Hopefully,Web services can make it much easier for applications to communicate.

Why WebServices?

Afew years ago Web services were not fast enough to be interesting.

Thanks tothe major IT development the last few years, most people and companies havebroadband connection and use the web more and more.

Interoperabilityhas highest priority.

When allmajor platforms could access the Web using Web browsers, different platformscould interact. For these platforms to work together, Web applications weredeveloped.
Webapplications are simple applications run on the web. These are built around theWeb browser standards and can mostly be used by any browser on any platform.

Webservices take Web applications to the next level.

Using Webservices your application can publish its function or message to the rest ofthe world.
Webservices uses XML to code and decode your data and SOAP to transport it usingopen protocols.
With Webservices your accounting departments Win 2k servers billing system can connectwith your IT suppliers UNIX server.

Webservices have two types of uses.

Reusableapplication components
There arethings different applications need very often. So why make these over and overagain?
Webservices can offer application components like currency conversion, weatherreports or even language translation as services.
Ideally,there will only be one type of each application component, and anyone can useit in their application.
Connectexisting software
Webservices help solve the interoperability problem by giving differentapplications a way to link their data.
Using Webservices you can exchange data between different applications and differentplatforms.

WebServices Platform Elements

WebServices have three basic platform elements.

Theseare called SOAP, WSDL and UDDI.

What isSOAP?

Thebasic Web services platform is XML plus HTTP.

SOAP stands for Simple Object Access Protocol
SOAP is a communication protocol
SOAP is for communication between applications
SOAP is a format for sending messages
SOAP is designed to communicate via Internet
SOAP is platform independent
SOAP is language independent
SOAP is based on XML
SOAP is simple and extensible
SOAP allows you to get around firewalls
SOAP will be developed as a W3C standard

What isWSDL?

WSDL isan XML-based language for describing Web services and how to access them.

WSDL stands for Web Services Description Language
WSDL is written in XML
WSDL is an XML document
WSDL is used to describe Web services
WSDL is also used to locate Web services
WSDL is not yet a W3C standard

What isUDDI?

UDDI isa directory service where businesses can register and search for Web services.

UDDI stands for Universal Description, Discovery and Integration
UDDI is a directory for storing information about web services
UDDI is a directory of web service interfaces described by WSDL
UDDI communicates via SOAP
UDDI is built into the Microsoft .NET platform

WebService Example

Anyapplication can have a Web Service component.

WebServices can be created regardless of programming language.

Anexample ASP.NET Web Service

In thisexample we use ASP.NET to create a simple Web Service.

<%@ WebService Language="VBScript" Class="TempConvert" %>

Imports System

Imports System.Web.Services

Public Class TempConvert :Inherits WebService

 Public Function FahrenheitToCelsius

(ByVal Fahrenheit As String) As String

dim fahr

fahr=trim(replace(Fahrenheit,",","."))

if fahr="" or IsNumeric(fahr)=false then return "Error"

return ((((fahr) - 32) / 9) * 5)

end function

 Public Function CelsiusToFahrenheit

(ByVal Celsius As String) As String

dim cel

cel=trim(replace(Celsius,",","."))

if cel="" or IsNumeric(cel)=false then return "Error"

return ((((cel) * 9) / 5) + 32)

end function

end class

Thisdocument is a .asmx file. This is the ASP.NET file extension for XML WebServices.

To runthis example you will need a .NET server.
The firstline in this document that it is a Web Service, written in VBScript and theclass name is "TempConvert":

<%@ WebService Language="VBScript" Class="TempConvert" %>

The nextlines imports the namespace "System.Web.Services" from the .NETframework.

Imports System

Imports System.Web.Services

The nextline defines that the "TempConvert" class is a WebService class type:

Public Class TempConvert :Inherits WebService

The nextstep is basic VB programming. This application has two functions. One toconvert from Fahrenheit to Celsius, and one to convert from Celsius to Fahrenheit.
The onlydifference from a normal application is that this function is defined as a"WebMethod".
Use"WebMethod" to mark the functions in your application that you wouldlike to make into web services.

 Public Function FahrenheitToCelsius

(ByVal Fahrenheit As String) As String

  dim fahr

  fahr=trim(replace(Fahrenheit,",","."))

  if fahr="" or IsNumeric(fahr)=false then return "Error"

  return ((((fahr) - 32) / 9) * 5)

end function

 Public Function CelsiusToFahrenheit

(ByVal Celsius As String) As String

  dim cel

  cel=trim(replace(Celsius,",","."))

  if cel="" or IsNumeric(cel)=false then return "Error"

  return ((((cel) * 9) / 5) + 32)

end function

The lastthing to do is to end the class:

end class

If yousave this as an .asmx file and publish it on a server with .NET support, youshould have your first working Web Service. Like our exampleWeb Service

ASP.NETautomates the process

WithASP.NET you do not have to write your own WSDL and SOAP documents.
If youlook closer on our example Web Service. You will see that the ASP.NET hasautomatically created a WSDLand SOAP request.

WebService Use

Usingyour example ASP.NET Web Service

In theprevious example we created an exampleWeb Service.
TheFahrenheit to Celsius function can be tested here: FahrenheitToCelsius.
TheCelsius to Fahrenheit function can be tested here: CelsiusToFahrenheit.

Thesefunctions will send you a XML reply.
Thesetests use HTTP POST and will send a XML response like this:

Use aform to access a Web Service.
Using aform and HTTP POST, you can put the web service on your site, like this:

Use aform to access the Web Service.
Here isthe code to add the Web Service to a web page:



method="POST"> 
  
    
    
  
  
    
    
  
Fahrenheit to Celsius:     size="30" name="Fahrenheit">
     value="Submit" class="button">



method="POST"> 
  
    
    
  
  
    
    
  
Celsius to Fahrenheit:     size="30" name="Celsius">
     value="Submit" class="button">

Substitute the www.example.com in the code above with the name of your website.

You HaveLearned Web Services, Now What?

WebServices Summary

Thistutorial has taught you how to convert your applications into web-applications.
You havelearned how to use XML to send messages between applications.
You havealso learned how to export a function (create a web service) from yourapplication.

Now YouKnow Web Services, What's Next?

The nextstep is to learn about WSDL and SOAP.
WSDL
WSDL is anXML-based language for describing Web services and how to access them.
WSDLdescribes a web service, along with the message format and protocol details forthe web service.
If youwant to learn more about WSDL, please visit our WSDL tutorial.
SOAP
SOAP is asimple XML-based protocol that allows applications to exchange information overHTTP.
Or moresimply: SOAP is a protocol for accessing a web service.
If youwant to learn more about SOAP, please visit our SOAP tutorial.

WSDLTutorial

WSDL (Web Services Description Language) is an XML-based language for describing Web services and how to access them.
Start learning WSDL!

Introduction to WSDL
This introduction to WSDL explains what WSDL is.
WSDL Documents
This chapter explains the main parts of an WSDL document.
WSDL Ports
This chapter explains the WSDL port interface.
WSDL Binding
This chapter explains the WSDL binding interface.
WSDL and UDDI
This chapter explains how UDDI (Universal Description Discovery andIntegration) is integrated with WSDL.
WSDL Syntax
The full WSDL syntax as listed in the W3C note.
WSDL Summary
This chapter contains a recommendation on what subject you should study afterthe WSDL tutorial.

Introductionto WSDL

WSDLis an XML-based language for describing Web services and how to access them.

What YouShould Already Know

Before youcontinue you should have a basic understanding of the following:

XML
XML Namespaces
XML Schema

If youwant to study these subjects first, find the tutorials on our Home page.

What isWSDL?

WSDL stands for Web Services Description Language
WSDL is written in XML
WSDL is an XML document
WSDL is used to describe Web services
WSDL is also used to locate Web services
WSDL is not yet a W3C standard

WSDLDescribes Web Services

WSDLstands for Web Services Description Language.
WSDL is adocument written in XML. The document describes a Web service. It specifies thelocation of the service and the operations (or methods) the service exposes.

WSDLDevelopment History at W3C

WSDL 1.1was submitted as a W3C Note by Ariba, IBM and Microsoft for describing servicesfor the W3C XML Activity on XML Protocols in March 2001.
(a W3CNote is made available by the W3C for discussion only. Publication of a Note byW3C indicates no endorsement by W3C or the W3C Team, or any W3C Members)
The firstWorking Draft of WSDL 1.2 was released by W3C in July 2002.
Go to our W3C Tutorial to read more aboutspecification status and timeline.

WSDLDocuments

AWSDL document is just a simple XML document.

Itcontains set of definitions to describe a web service.

The WSDLDocument Structure

A WSDLdocument describes a web service using these major elements:

Element	Defines
	The operations performed by the web service
	The messages used by the web service
	The data types used by the web service
	The communication protocols used by the web service

The mainstructure of a WSDL document looks like this:

   definition of types........

   definition of a message....

   definition of a port.......

   definition of a binding....

A WSDLdocument can also contain other elements, like extension elements and a serviceelement that makes it possible to group together the definitions of several webservices in one single WSDL document.
For acomplete syntax overview go to the chapter WSDL Syntax.

WSDLPorts

The element is the most important WSDL element.
Itdescribes a web service, the operations that can be performed, and the messagesthat are involved.
The element can be compared to a function library (or a module, ora class) in a traditional programming language.

WSDLMessages

The element defines the data elements of an operation.
Eachmessage can consist of one or more parts. The parts can be compared to the parametersof a function call in a traditional programming language.

WSDLTypes

The element defines the data type that are used by the web service.
Formaximum platform neutrality, WSDL uses XML Schema syntax to define data types.

WSDLBindings

The element defines the message format and protocol details for each port.

WSDLExample

This is asimplified fraction of a WSDL document:

In thisexample the element defines "glossaryTerms"as the name of a port, and "getTerm" as the name of an operation.
The"getTerm" operation has an input message called"getTermRequest" and an output message called"getTermResponse".
The elements define the parts of each message and theassociated data types.
Comparedto traditional programming, glossaryTerms is a function library,"getTerm" is a function with "getTermRequest" as the inputparameter and getTermResponse as the return parameter

AWSDL port describes the interfaces (legal operations) exposed by a web service.

WSDLPorts

The element is the most important WSDL element.
It definesa web service, the operations that can be performed, and the messagesthat are involved.
The portdefines the connection point to a web service. It can be compared to a functionlibrary (or a module, or a class) in a traditional programming language. Eachoperation can be compared to a function in a traditional programming language.

OperationTypes

The request-responsetype is the most common operation type, but WSDL defines four types:

Type	Definition
One-way	The operation can receive a message but will not return a response
Request-response	The operation can receive a request and will return a response
Solicit-response	The operation can send a request and will wait for a response
Notification	The operation can send a message but will not wait for a response

One-WayOperation

A one-wayoperation example:

In thisexample the port "glossaryTerms" defines a one-way operation called"setTerm".
The"setTerm" operation allows input of new glossary terms messages usinga "newTermValues" message with the input parameters "term"and "value". However, no output is defined for the operation.

Request-ResponseOperation

Arequest-response operation example:

In thisexample the port "glossaryTerms" defines a request-response operationcalled "getTerm".
The"getTerm" operation requires an input message called"getTermRequest" with a parameter called "term", and willreturn an output message called "getTermResponse" with a parametercalled "value".

WSDLBindings

WSDLbindings defines the message format and protocol details for a web service.

Bindingto SOAP

Arequest-response operation example:

transport="http://schemas.xmlsoap.org/soap/http" />

     soapAction="http://example.com/getTerm"/>

Thebinding element has two attributes - the name attribute and the typeattribute.
The nameattribute (you can use any name you want) defines the name of the binding, andthe type attribute points to the port for the binding, in this case the"glossaryTerms" port.
The soap:bindingelement has two attributes - the style attribute and the transport attribute.
The styleattribute can be "rpc" or "document". In this case we usedocument. The transport attribute defines the SOAP protocol to use. In thiscase we use HTTP.
Theoperation element defines each operation that the port exposes.
For eachoperation the corresponding SOAP action has to be defined. You must alsospecify how the input and output are encoded. In this case we use"literal".

WSDLand UDDI

UniversalDescription, Discovery and Integration (UDDI) is a directory service wherebusinesses can register and search for Web services.

What isUDDI

UDDI is aplatform-independent framework for describing services, discovering businesses,and integrating business services by using the Internet.

UDDI stands for Universal Description, Discovery and Integration
UDDI is a directory for storing information about web services
UDDI is a directory of web service interfaces described by WSDL
UDDI communicates via SOAP
UDDI is built into the Microsoft .NET platform

What isUDDI Based On?

UDDI usesWorld Wide Web Consortium (W3C) and Internet Engineering Task Force (IETF)Internet standards such as XML, HTTP, and DNS protocols.
UDDI usesWSDL to describe interfaces to web services
Additionally,cross platform programming features are addressed by adopting SOAP, known asXML Protocol messaging specifications found at the W3C Web site.

UDDIBenefits

Anyindustry or businesses of all sizes can benefit from UDDI
BeforeUDDI, there was no Internet standard for businesses to reach their customersand partners with information about their products and services. Nor was therea method of how to integrate into each other's systems and processes.

Problems the UDDI specification can help to solve:

Making it possible to discover the right business from the millions currently online
Defining how to enable commerce once the preferred business is discovered
Reaching new customers and increasing access to current customers
Expanding offerings and extending market reach
Solving customer-driven need to remove barriers to allow for rapid participation in the global Internet economy
Describing services and business processes programmatically in a single, open, and secure environment

How canUDDI be Used

Ifthe industry published an UDDI standard for flight rate checking andreservation, airlines could register their services into an UDDI directory.Travel agencies could then search the UDDI directory to find the airline's reservationinterface. When the interface is found, the travel agency can communicate withthe service immediately because it uses a well-defined reservation interface.

Who isSupporting UDDI?

UDDI is across-industry effort driven by all major platform and software providers likeDell, Fujitsu, HP, Hitachi, IBM, Intel, Microsoft, Oracle, SAP, and Sun, aswell as a large community of marketplace operators, and e-business leaders.
Over 220companies are members of the UDDI community.

TheFull WSDL Syntax

Thefull WSDL 1.2 syntax as described in the W3C Working Draft is listed below.

        <-- binding details --> *

            <-- binding details --> *

                <-- binding details -->

                <-- binding details --> *

                <-- binding details --> *

            <-- address details -->

YouHave Learned WSDL, Now What?

WSDLSummary

Thistutorial has taught you how to create WSDL documents that describes a webservice. It also specifies the location of the service and the operations (ormethods) the service exposes.
You havelearned how to define the message format and protocol details for a webservice.
You havealso learned that you can register and search for web services with UDDI.

Now YouKnow WSDL, What's Next?

The nextstep is to learn about SOAP and Web Services.
SOAP
SOAP is asimple XML-based protocol that allows applications to exchange information overHTTP.
Or moresimply: SOAP is a protocol for accessing a web service.
If youwant to learn more about SOAP, please visit our SOAP tutorial.
WebServices
Webservices can convert your applications into web-applications.
By usingXML, Messages can be sent between applications.
If youwant to learn more about web services, please visit our Web Services tutorial

.NET WebServices

Webservices are small units of code built to handle a limited task.

What areWeb Services?

Web services are small units of code
Web services are designed to handle a limited set of tasks
Web services use XML based communicating protocols
Web services are independent of operating systems
Web services are independent of programming languages
Web services connect people, systems and devices

SmallUnits of Code

Webservices are small units of code designed to handle a limited set of tasks.
An exampleof a web service can be a small program designed to supply other applicationswith the latest stock exchange prices. Another example can be a small programdesigned to handle credit card payment.

XML BasedWeb Protocols

Webservices use the standard web protocols HTTP, XML, SOAP, WSDL, and UDDI.

HTTP

HTTP(Hypertext Transfer Protocol) is the World Wide Web standard for communicationover the Internet. HTTP is standardized by the World Wide Web Consortium (W3C).

XML

XML(eXtensible Markup Language) is a well known standard for storing, carrying,and exchanging data. XML is standardized by the W3C.
You canread more about XML in our XMLtutorial.

SOAP

SOAP(Simple Object Access Protocol) is a lightweight platform and language neutralcommunication protocol that allows programs to communicate via standardInternet HTTP. SOAP is standardized by the W3C.
You canread more about SOAP in our SOAPtutorial.

WSDL

WSDL (WebServices Description Language) is an XML-based language used to define webservices and to describe how to access them. WSDL is a suggestion by Ariba, IBMand Microsoft for describing services for the W3C XML Activity on XMLProtocols.
You canread more about WSDL in our WSDLtutorial.

UDDI

UDDI(Universal Description, Discovery and Integration) is a directory service wherebusinesses can register and search for web services.
UDDI is apublic registry, where one can publish and inquire about web services.

Independentof Operating Systems

Since webservices use XML based protocols to communicate with other systems, webservices are independent of both operating systems and programming languages.
Anapplication calling a web service will always send its requests using XML, andget its answer returned as XML. The calling application will never be concernedabout the operating system or the programming language running on the othercomputer.

Benefitsof Web Services

Easier to communicate between applications
Easier to reuse existing services
Easier to distribute information to more consumers
Rapid development

Webservices make it easier to communicate between different applications. Theyalso make it possible for developers to reuse existing web services instead ofwriting new ones.
Webservices can create new possibilities for many businesses because it providesan easy way to distribute information to a large number of consumers. Oneexample could be flight schedules and ticket reservation systems.

Lokesh sharma

asp.net interview questions and answers

Web Services Interview Questions and answers

What is SOAP?

Simple ObjectAccess Protocol (SOAP) is a lightweight protocol for exchange of information ina decentralized, distributed environment. It's an industry-standard messageformat that enables message-based communications for Web services.

2. What is UDDI?

3. What is WSDL?

Web ServiceDescription Language (WSDL) defines an XML grammar for describing web services.This description includes details such as where to find the web service (itsURL), what methods and properties that service supports, the data types and theprotocols used to communicate with the service.

4. Describe Web Service (XML Web Service)?

5. Give examples of a WebService?

6. What is SOAP Protocol message contains?

A SOAP Protocolmessage contains four parts:

· An envelope

· Encoding Rules

· RPC representation(Convention)

· Protocol binding(optional)

Introductionto Web Services

What YouShould Already Know

What areWeb Services?

How Doesit Work?

TheFuture of Web services

Why WebServices?

Interoperabilityhas highest priority.

Webservices take Web applications to the next level.

Webservices have two types of uses.

WebServices Platform Elements

What isSOAP?

What isWSDL?

What isUDDI?

WebService Example

Anexample ASP.NET Web Service

ASP.NETautomates the process

WebService Use

Usingyour example ASP.NET Web Service

You HaveLearned Web Services, Now What?

WebServices Summary

Now YouKnow Web Services, What's Next?

WSDLTutorial

WSDLTutorial

Table ofContents

Introductionto WSDL

What YouShould Already Know

What isWSDL?

WSDLDescribes Web Services

WSDLDevelopment History at W3C

WSDLDocuments

The WSDLDocument Structure

WSDLPorts

WSDLMessages

WSDLTypes

WSDLBindings

WSDLExample

WSDLPorts

OperationTypes

One-WayOperation

Request-ResponseOperation

WSDLBindings

Bindingto SOAP

WSDLand UDDI

What isUDDI

What isUDDI Based On?

UDDIBenefits

How canUDDI be Used

Who isSupporting UDDI?

TheFull WSDL Syntax

YouHave Learned WSDL, Now What?

WSDLSummary

Now YouKnow WSDL, What's Next?

.NET WebServices

What areWeb Services?

SmallUnits of Code

XML BasedWeb Protocols

HTTP

XML

SOAP

WSDL

UDDI

Independentof Operating Systems

Benefitsof Web Services