Using .NET Framework 3.5 C#, I am in the process of moving from SOAP-based Web Services to JSON-based WCF Services. All my web services derive from a common ServiceBase class with common functionality like session validation, client authentication, database connection, logging etc. and in all my web service method I call a common method on the base class using a single line of code to perform the common tasks
base.InitCallThread()
Q1: What is the best way to do the same or similar in WCF in order to avoid having to write hundreds of lines of repetitive code?
Q2: If I was to support the same interfaces with both SOAP-based Web Services and JSON-based WCF services in parallel, what would be the best way to share the same common functionality? I guess it is possible to share the http session b/w the two?
You should refactor your base class code into a separate class. Call that separate class from the base class in your ASMX services; in the WCF service, call it from each individual service, or use one of the WCF extensibility mechanisms to call it centrally.
WCF permits the same service to be exposed on multiple endpoints with different bindings. You can expose the same WCF service with basicHttpBinding for SOAP, at the same time as exposing a webHttpBinding for the JSON.
Q1: You can derive from the same ServiceBase class with common functionality as you had before. WCF does not limit you in this matter. It requires only implementing some interface
Q2: You can define multiple bindings through web.config (or programmatic) configuration.
Related
Is there any possibility as a client to get a list of contracts a WCF host exposes?
I would like to query a service and to ask what interfaces it implements.
Take a look at WCF Discovery.
This is not supported by WCF.
You can query the service's WSDL contract, but not the WCF contracts or any Interfaces.
The best you will be able to do is to see what is exposed, and assume that is the interface. You will not be able to see all the different interfaces that the class implements. For example, if you had a service which implemented IFooService, and IDisposable, with IFooService exposed through WCF, you would be able to see all the methods of IFooService from the client.
The WCF Test utility will take a given wsdl and generate a client for it, looking at the source for that might be a good starting point. (you'll have to decompile it with something like reflector)
Another idea, You could programatically invoke svcutil to generate a client for a given wsdl, then invoke msbuild to compile it, and use reflection to load the output assembly. It would be a fairly large amount of work, and I'm not sure what you would do with it. You would have to build a fairly complex UI to inspect and invoke the client.
In general (web) services are being described by XML-based protocols such as WSDL. This is used both for discovery of the services and for describing their operations. Also UDDI is sometimes used but mostly for Enterprise Application Integration (internal use).
So you can have your WCF service produce WSDL information and let your client query that.
What benefits does WCF bring to the table and why should I use this new technology over good old ASP.Net web services?
Maybe you don't need to transition to WCF if regular Web-Service will work for you,
however WCF encompasses more than just Web-Services.
With WCF you can utilize different communication channels (such as Web-Services, MSMQ, named pipes...) utilizing the same end-point service handler code.
WCF also has different built-in security mechanisms, allows you to utilize different serialization mechanisms (if something other than Soap is needed like raw JSON), hosting of services without the requirement of needing a web project etc...
As such WCF is more a general service hosting framework that can replace regular ASMX web services
Here is a good article from msdn that talks about the differences between ASMX and WCF
A few key areas
Serialization - Asmx uses XmlSerializer while WCF uses the DataContractSerializer. The Datacontract serializer is about 10% faster (source along with other information)
Differences Between ASMX and WCF Services
Greater protocol support (HTTP, TCP, ICP, MSMQ for WCF), ASMX only supports HTTP
I have an existing WCF service.
Is it possible to add operation contract to the service interface and have the implementation in a workflow?
Or I absolutly need a seperate service interface for my workflow?
When you publish a WCF service you are publishing the interface and telling it what implementation to use. You can specify only one implementation, otherwise how would WCF know where to route which request. So in short you need to use a separate interface for your workflow services. That said, if you don't want to change your public facing API there is no reason you can't create a minimal implementation that just passes request on to your worklflow service.
What is the difference between them?
When would I opt for one over the other?
This answer is based on an article that no longer exists:
Summary of article:
"Basically, WCF is a service layer that allows you to build applications that can communicate using a variety of communication mechanisms. With it, you can communicate using Peer to Peer, Named Pipes, Web Services and so on.
You can’t compare them because WCF is a framework for building interoperable applications. If you like, you can think of it as a SOA enabler. What does this mean?
Well, WCF conforms to something known as ABC, where A is the address of the service that you want to communicate with, B stands for the binding and C stands for the contract. This is important because it is possible to change the binding without necessarily changing the code. The contract is much more powerful because it forces the separation of the contract from the implementation. This means that the contract is defined in an interface, and there is a concrete implementation which is bound to by the consumer using the same idea of the contract. The datamodel is abstracted out."
... later ...
"should use WCF when we need to communicate with other communication technologies (e,.g. Peer to Peer, Named Pipes) rather than Web Service"
From What's the Difference between WCF and Web Services?
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 Microsoft. 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 Microsoft; 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.
The major difference is that Web Services Use XmlSerializer. But WCF Uses DataContractSerializer which is better in performance as compared to XmlSerializer.
Web Service
is based on SOAP and return data in XML form.
It support only HTTP protocol.
It is not open source but can be consumed by any client that understands xml.
It can be hosted only on IIS.
WCF
is also based on SOAP and return data in XML form.
It is the evolution of the web service(ASMX) and support various protocols like TCP, HTTP, HTTPS, Named Pipes, MSMQ.
The main issue with WCF is, its tedious and extensive configuration.
It is not open source but can be consumed by any client that understands xml.
It can be hosted with in the applicaion or on IIS or using window service.
Basic and primary difference is, ASP.NET web service is designed to exchange SOAP messages over HTTP only while WCF Service can exchange message using any format (SOAP is default) over any transport protocol i.e. HTTP, TCP, MSMQ or NamedPipes etc.
What is the difference between web service and WCF?
Web service use only HTTP protocol while transferring data from one application to other application.
But WCF supports more protocols for transporting messages than ASP.NET Web services. WCF supports sending messages by using HTTP, as well as the Transmission Control Protocol (TCP), named pipes, and Microsoft Message Queuing (MSMQ).
To develop a service in Web Service, we will write the following code
[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;
}
}
Web Service is not architecturally more robust. But WCF is architecturally
more robust and promotes best practices.
Web Services use XmlSerializer but WCF uses DataContractSerializer. Which is
better in performance as compared to XmlSerializer?
For internal (behind firewall) service-to-service calls we use the net:tcp
binding, which is much faster than SOAP.
WCF is 25%—50% faster than ASP.NET Web Services, and approximately 25%
faster than .NET Remoting.
When would I opt for one over the other?
WCF is used to communicate between other applications which has been developed on other platforms and using other Technology.
For example, if I have to transfer data from .net platform to other application which is running on other OS (like Unix or Linux) and they are using other transfer protocol (like WAS, or TCP) Then it is only possible to transfer data using WCF.
Here is no restriction of platform, transfer protocol of application while transferring the data between one application to other application.
Security is very high as compare to web service
The major difference is time-out, WCF Service has timed-out when there is no response, but web-service does not have this property.
I'm looking to understand when to use a WCF services instead of just using webclient or httpwebrequest. I guess I'm also looking to understand the difference between the design patterns that would be appropriate for both.
Are you talking about when to create a WCF service yourself (over web service), or when to consume an existing web service using WCF instead of .NET 2.0 ASMX clients?
As for creating a WCF service yourself:
Gives you a lot more options in terms of hosting (in an app, Windows Service, IIS, WAS)
Gives you a lot more security options
Gives you a lot more protocol options (besides just HTTP, you can also use WS-*, TCP, Named Pipes, MSMQ and more)
Allows you to write your service once, and expose it on multiple end-points with different protocols at the same time
As for using WCF to talk to an existing HTTP (ASMX) web service - I don't see a whole lot of massive benefits, except WCF uses more configuration over code, and it can be good to standardize on one way of doing things, if you already use other WCF services, anyway.
Marc
I'm currently using WCF for most of the things that I would use WebClient or HttpWebRequest/HttpWebResponse in the past. While there definitely is overhead for learing how to make calls to web methods using WCF, the extensibility of WCF and the abstraction it provides makes it a MUCH better candidate for these types of calls.
I've already used it to make calls to Akismet and RPX pretty easily.
To get started, I'd look at the section of the MSDN documentation titled "WCF Web Programming Object Model", located at:
http://msdn.microsoft.com/en-us/library/bb412204.aspx