In this article I will explain the Difference between ASP.NET web service and
WCF services like ASP.NET web services. I will also discusses how we use the
both technologies for developing the web services.
Web Service in ASP.net:
A Web Service is programmable application logic accessible via standard Web
protocols. One of these Web protocols is the Simple Object Access Protocol
(SOAP). SOAP is a W3C submitted note (as of May 2000) that uses standards based
technologies (XML for data description and HTTP for transport) to encode and
transmit application data.
Consumers of a Web Service do not need to know anything about the platform,
object model, or programming language used to implement the service; they only
need to understand how to send and receive SOAP messages (HTTP and XML).
WCF Service:
Windows Communication Foundation (WCF) is a framework for building
service-oriented applications. Using WCF, you can send data as asynchronous
messages from one service endpoint to another. A service endpoint can be part of
a continuously available service hosted by IIS, or it can be a service hosted in
an application. An endpoint can be a client of a service that requests data from
a service endpoint. The messages can be as simple as a single character or word
sent as XML, or as complex as a stream of binary data.
In what scenarios WCF must be used:
- A secure service to process business
transactions.
- A service that supplies current data to
others, such as a traffic report or other monitoring service.
- A chat service that allows two people to
communicate or exchange data in real time.
- A dashboard application that polls one or
more services for data and presents it in a logical presentation.
- Exposing a workflow implemented using
Windows Workflow Foundation as a WCF service.
- A Silverlight application to poll a
service for the latest data feeds.
Features of WCF:
- Service Orientation
- Interoperability
- Multiple Message Patterns
- Service Metadata
- Data Contracts
- Security
- Multiple Transports and Encodings
- Reliable and Queued Messages
- Durable Messages
- Transactions
- AJAX and REST Support
- Extensibility
Difference between Web Service in ASP.net &
WCF Service:
WCF is a replacement for all earlier web service technologies from Microsoft. It
also does a lot more than what is traditionally considered as "web services".
WCF "web services" are part of a much broader spectrum of remote communication
enabled through WCF. You will get a much higher degree of flexibility and
portability doing things in WCF than through traditional ASMX because WCF is
designed, from the ground up, to summarize all of the different distributed
programming infrastructures offered by MS. An endpoint in WCF can be
communicated with just as easily over SOAP/XML as it can over TCP/binary and to
change this medium is simply a configuration file mod. In theory this reduces
the amount of new code needed when porting or changing business needs, targets,
etc.
ASMX is older than WCF, and anything ASMX can do so can WCF (and more).
Basically you can see WCF as trying to logically group together all the
different ways of getting two apps to communicate in the world of MS; ASMX
was just one of these many ways and so is now grouped under the WCF umbrella of
capabilities.
Web Services can be accessed only over HTTP & it works in stateless environment,
where WCF is flexible because its services can be hosted in different types of
applications. Common scenarios for hosting WCF services are IIS ,WAS
,Self-hosting ,Managed Windows Service.
Major Difference is That Web Services Use XmlSerializer But WCF Uses
DataContractSerializer which is better in Performance as Compared to
XmlSerializer.
Key issues with XmlSerializer to serialize .NET types to XML
- Only Public fields or Properties of .NET
types can be translated into XML.
- Only the classes which implement
IEnumerable interface.
- Classes that implement the IDictionary
interface, such as Hash table can not be serialized.
Important difference between
DataContractSerializer and XMLSerializer.
- A practical benefit of the design of the
DataContractSerializer is better performance over Xmlserializer.
- XML Serialization does not indicate the
which fields or properties of the type are serialized into XML where as
DataCotratSerializer Explicitly shows the which fields or properties are
serialized into XML.
- The DataContractSerializer can translate
the HashTable into XML.
![wcf.gif]()
The development of web service with ASP.NET
relies on defining data and relies on the XmlSerializer to transform data to or
from a service.
Key issues with XmlSerializer to serialize .NET types to XML
- Only Public fields or Properties of .NET
types can be translated into XML.
- Only the classes which implement
IEnumerable interface.
- Classes that implement the IDictionary
interface, such as Hash table can not be serialized.
The WCF uses the DataContractAttribute and
DataMemeberAttribute to translate .NET FW types in to XML.
[DataContract]
public
class Item
{
[DataMember]
public
string ItemID;
[DataMember]
public
decimal ItemQuantity;
[DataMember]
public
decimal ItemPrice;
}
The DataContractAttribute can be applied to the
class or a strcture.DataMemberAttribute can be applied to field or a property
and theses fields or properties can be either public or private.
Important difference between DataContractSerializer and XMLSerializer.
- A practical benefit of the design of the
DataContractSerializer is better performance over XMLserialization.
- XMLSerialization does not indicate the
which fields or properties of the type are serialized into XML where as
DataCotratSerializer Explicitly shows the which fields or properties are
serialized into XML.
- The DataContractSerializer can translate
the HashTable into XML.
Developing Service
To develop a service using ASP.NET we must add the WebService attribute to the
class and WebMethodAttribute to any of the class methods.
Example
[WebService]
public
class Service :
System.Web.Services.WebService
{
[WebMethod]
public string Test(string strMsg)
{
return strMsg;
}
}
To develop a service in WCF we will write the following code
[ServiceContract]
public
interface ITest
{
[OperationContract]
string ShowMessage(string strMsg);
}
public
class Service : ITest
{
public string
ShowMessage(string strMsg)
{
return strMsg;
}
}
The ServiceContractAttribute specifies that a
interface defines a WCF service contract, OperationContract Attribute indicates
which of the methods of the interface defines the operations of the service
contract.
A class that implements the service contract is referred to as a service type in
WCF.
Hosting the Service
ASP.NET web services are compiled into a class library assembly and a service
file with an extension .asmx will have the code for the service. The service
file is copied into the root of the ASP.NET application and Assembly will be
copied to the bin directory. The application is accessible using url of the
service file.
WCF Service can be hosted within IIS or WindowsActivationService.
• Compile the service type into a class library
• Copy the service file with an extension .SVC into a virtual directory and
assembly into bin sub directory of the virtual directory.
• Copy the web.config file into the virtual directory.
Client Development
Clients for the ASP.NET Web services are generated using the command-line tool
WSDL.EXE.
WCF uses the ServiceMetadata tool(svcutil.exe) to generate the client for the
service.
Message Representation
The Header of the SOAP Message can be customized in ASP.NET Web service.
WCF provides attributes MessageContractAttribute , MessageHeaderAttribute and
MessageBodyMemberAttribute to describe the structure of the SOAP Message.
Service Description
Issuing a HTTP GET Request with query WSDL causes ASP.NET to generate WSDL to
describe the service. It returns the WSDL as response to the request.
The generated WSDL can be customized by deriving the class of
ServiceDescriptionFormatExtension.
Issuing a Request with the query WSDL for the .svc file generates the WSDL. The
WSDL that generated by WCF can customized by using ServiceMetadataBehavior
class.
Exception Handling
In ASP.NET Web services, Unhandled exceptions are returned to the client as SOAP
faults.
In WCF Services, unhandled exceptions are not returned to clients as SOAP
faults. A configuration setting is provided to have the unhandled exceptions
returned to clients for the purpose of debugging.