Can somebody please explain me the main use of data contract.
I am not very much clear definitions given on MSDN and many more website Can you please explain me with a scenario or example so that it can be understood in a better way.
Thanks,
Monika
I would recommend you a book i used to learn the basics and understand how WCF works and what are the contracts and what are the differences between them.
Wrox - Professional WCF 4: Windows Communication Foundation with .NET 4
It's a great book and easy to understand and has a lot of examples for you.
DataContract is used on a class and DataMemeber is used on it's properties so when you call the WCF service it uses this Contracts to serialize and send your class between the Client and Server side. With the Contracts your Client side can use then the class and it's data.
I want to create a WCF service. What is the best design pattern to do this?
For example three seperated projects like this:
1) DataContract
2) BusinessLogic
3) SvcHostProject
That doesn't sound too bad, although I'd probably combine the DataContract and the SvcHostProject as they would both have to reference the WCF binaries and seem to share the same coarse-grained responsibility (that is, unless you are thinking about creating a general-purpose ServiceHost).
You might want to see the (old) post about making WCF services more testable: http://blogs.msdn.com/b/ploeh/archive/2008/07/12/an-overview-of-unit-testing-duplex-wcf-services-and-clients.aspx Although it talks about duplex services, you can easily extrapolate how to deal with more 'normal' request-response services as well.
This article helped me a lot http://www.netfxharmonics.com/2008/11/Architectural-Overview-Creating-Streamlined-Simplified-yet-Scalable-WCF-Connectivity
When I went to University, teachers used to say that in good structured application you have presentation layer, business layer and data layer. This is what I heard for more than 5 years.
When I started working I discovered that this is true but sometimes is better to have more than just three layers. Two or three days ago I discovered this article by John Papa that explain how to use Entity Framework in layered application. According to that article you should have:
UI Layer and Presentation Layer (Model View Pattern)
Service Layer (WCF)
Business Layer
Data Access Layer
Service Layer is, to me, one of the best ideas I've ever heard since I work. Your UI is then completely "diconnected" from Business and Data Layer. Now when I went deeper by looking into provided source code, I began to have some questions. Can you help me in answering them?
Question #0: is this a good enterpise application template in your opinion?
Question #1: where should I host the service layer? Should it be a Windows Service or what else?
Question #2: in the source code provided the service layer expose just an endpoint with WSHttpBinding. This is the most interoperable binding but (I think) the worst in terms of performances (due to serialization and deserializations of objects). Do you agree?
Question #3: if you agree with me at Question 2, which kind of binding would you use?
Looking forward to hear from you. Have a nice weekend!
Marco
Question #0: is this a good enterpise
application template in your opinion?
Yes, for most middle-of-the-road line-of-business applications, it's probably a good starting point.
Question #1: where should I host the
service layer? Should it be a Windows
Service or what else?
If you're serious about using WCF services, then yes, I would recommend self-hosting them in a Windows service. Why? You don't have to have IIS on the server, you don't have to rely on IIS to host your service, you can choose your service address as you wish, and you have complete control over your options.
Question #2: in the source code
provided the service layer expose just
an endpoint with WSHttpBinding. This
is the most interoperable binding but
(I think) the worst in terms of
performances (due to serialization and
deserializations of objects). Do you
agree?
No, the most interoperable would be a basicHttpBinding with no security. Any SOAP stack will be able to connect to that. Or then a webHttpBinding for a RESTful service - for this, you don't even need SOAP - just a HTTP stack will do.
What do we use??
internally, if Intranet-scenarios are in play (server and clients behind corporate firewall): always netTcp - it's the best, fastest, most versatile. Doesn't work well over internet though :-( (need to open ports on firewalls - always a hassle)
externally: webHttpBinding or basicHttpBinding, mostly because of their ease of integration with non-.NET platforms
Here are my 5 cents:
0: yes
1: I would start by hosting it in IIS because it's very easy and gets you somewhere fast.
2: If you need security then definitely yes, go with WSHttpBinding (or maybe even wsFederationHttpBinding if you want some more fance security). It performs quite fast in practice even though, as you say, it does have some overhead, and can be quite hard to call from other platforms (such as java).
3: N/A
Finally, remember to define your services' data-contract objects in a separate assembly that can be referenced both from the service dll and the consumer in your ui layer.
Did your teachers also tell you why you should create such an architecture ;-) ? What I am missing in your question are your requirements. Before any of us can tell you if this is a good architecture or template, we have to know the requirements of the application. The non functional requirements or -illities of an application should drive the design of an architecture.
I would like to know what is the most important non functional requirement of your application? (Maintainability, Portability, Reliability or ...). For example take a look at http://en.wikipedia.org/wiki/ISO/IEC_9126 or http://www.serc.nl/quint-book/
I think that we architects should create architectures based on requirements from the business. This means that we architects should make the business more aware of the importance of non functional requirements.
Question #0: is this a good enterpise application template in your opinion?
You use the layers architecture pattern, this means that layers could evolve independent of each other more easily. One of the most used architecture patterns, note that this pattern also has disadvantages (performance, traceability).
Question #1: where should I host the service layer? Should it be a Windows Service or what else?
Difficult to answer. Hosting a service in IIS has two advantages, it scales easier and traceability is easier (WCF in IIS has loads of monitor options). Hosting a service in a Windows Service gives you more binding options (Named Pipe binding/ TCP binding).
Question #2: in the source code provided the service layer expose just an endpoint with WSHttpBinding. This is the most interoperable binding but (I think) the worst in terms of performances (due to serialization and deserializations of objects). Do you agree?
Performance wise the WSHttpBinding costs more, but it scores high on interoperability. So the choice depends on your non-functional requirements.
Question #3: if you agree with me at Question 2, which kind of binding would you use?
Named Pipes and TCP binding are very fast. Name Pipe binding should only be used when communicating in a single machine. TCP binding could be an option but you have to open a special port in the firewall.
I know this question is old, but I found it while searching for my current architectural problem in refactoring a service layer that feeds a web application. While googling, I've found these much more modern guidelines by Microsoft, hoping that this could help somebody, here's the links:
about the business layer and the discouraged anemic domain model https://learn.microsoft.com/en-us/dotnet/architecture/microservices/microservice-ddd-cqrs-patterns/microservice-domain-model
about the data persistence layer
https://learn.microsoft.com/en-us/dotnet/architecture/microservices/microservice-ddd-cqrs-patterns/infrastructure-persistence-layer-design
The entire pattern book is downloadable as pdf.
[EDIT]
Through the documentation, I've found a technique, that in my experience has been useful to avoid lots of switch case and to apply powerful patterns to solve complex problems. The suggested implementation is better than mine (I had to use older c# versions): https://learn.microsoft.com/en-us/dotnet/architecture/microservices/microservice-ddd-cqrs-patterns/enumeration-classes-over-enum-types
On the MSDN we can read :
The WS2007HttpBinding class adds a system-provided binding similar to WSHttpBinding but uses the Organization for the Advancement of Structured Information Standards (OASIS) standard versions of the ReliableSession, Security, and TransactionFlow protocols. No changes to the object model or default settings are required when using this binding.
But I don't find any documentation which can explain me WHY I would like to move wsHttpBinding to ws2007HttpBinding, it seems to me that the standard are the same.
Can someone can give me a good explanation ?
The bindings support different protocols. This page on MSDN actually has a nice matrix that explains what protocols are supported by which binding in WCF. So if you need interop with services/clients that implement OASIS protocols, use the ws2007httpbinding binding, otherwise, there's no reason to not use the wshttpbinding.
If you want to get into details of the different protocols, check out their websites: WC3 and OASIS. I'm sure there's tons of resources that highlight the differences in those protocols.
Different large enterprise and governments needs to use web services and have different requirements. Thus, different standards make sense.
From OReilly book "Programming WCF services" (p.28-29) they say that Ws2007HttpBinding derives from the WsHttpBinding. It adds support for emerging standard and updates for the transaction, security and reliability standards.
Using the lastest standard sounds like a good practice, but just keep in mind that WS2007HttpBinding is only supported by clients that are running at least .NET runtime versions 3.5 SP1 or 3.0 SP1.
ws2007HttpBinding defined by OASIS is a newer version than wsHttpBinding.
It added ReliableSession, Security, and TransactionFlow protocols on top of Transactions, Reliable messaging, and WS-Addressing protocols of wsHttpBinding.
It could be easier to start with simple binding, and if required in the future, you can always expose the existing services in a newer binding coexisting with the older version.
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I understand the value of the three-part service/host/client model offered by WCF. But is it just me or does it seem like WCF took something pretty direct and straightforward (the ASMX model) and made a mess out of it?
Is there an alternative to using SvcUtil's command line step back in time to generate the proxy? With ASMX services a test harness was automatically provided; is there a good alternative today with WCF?
I appreciate that the WS* stuff is more tightly integrated with WCF and hope to find some payoff for WCF there, but geeze, otherwise I'm perplexed.
Also, the state of books available for WCF is abysmal at best. Juval Lowy, a superb author, has written a good O'Reilly reference book "Programming WCF Services" but it doesn't do that much (for me anyway) for learning now to use WCF. That book's precursor (and a little better organized, but not much, as a tutorial) is Michele Leroux Bustamante's Learning WCF. It has good spots but is outdated in place and its corresponding Web site is gone.
Do you have good WCF learning references besides just continuing to Google the bejebus out of things?
Okay, here we go. First, Michele Leroux Bustamante's book has been updated for VS2008. The website for the book is not gone. It's up right now, and it has tons of great WCF info. On that website she provides updated code compatible with VS2008 for all the examples in her book. If you order from Amazon, you will get the reprint which is updated.
WCF is not only a replacement for ASMX. Sure it can (and does quite well) replace ASMX, but the real benefit is that it allows your services to be self-hosted. Most of the functionality from WSE has been baked in from the start. The framework is highly configurable, and the ability to serve multiple endpoints over multiple protocols is amazing, IMO.
While you can still generate proxy classes from the "Add Service Reference" option, it's not necessary. All you really have to do is copy your ServiceContract interface and tell your code where to find the endpoint for the service, and that's it. You can call methods from the service with very little code. Using this method, you have complete control over the implementation. Regardless of the method you choose to generate a proxy class, Michele shows both and uses both in her excellent series of webcasts on the subject.
Michele has tons of great material out there, and I recommend you check out her website(s). Here's some links that were incredibly helpful for me as I was learning WCF. I hope that you'll come to realize how strong WCF really is, and how easy it is to implement. The learning curve is a little bit steep, but the rewards for your time investment are well worth it:
Michele's webcasts: http://www.dasblonde.net/2007/06/24/WCFWebcastSeries.aspx
Michele's book website (alive and updated for VS2008): http://www.thatindigogirl.com/
I recommend you watch at least 1 of Michele's webcasts. She is a very effective presenter, and she's obviously incredibly knowledgeable when it comes to WCF. She does a great job of demystifying the inner workings of WCF from the ground up.
I typically use Google to find my WCF answers and commonly find myself on the following blogs:
Blogs with valuable WCF articles
http://blogs.msdn.com/drnick/default.aspx
http://blogs.msdn.com/wenlong/default.aspx
http://blogs.thinktecture.com/buddhike/
http://www.dasblonde.net/default.aspx
Other valuable articles I've found
http://blogs.conchango.com/pauloreichert/archive/2007/02/22/WCF-Reliable-Sessions-Puzzle.aspx
http://blogs.msdn.com/salvapatuel/archive/2007/04/25/why-using-is-bad-for-your-wcf-service-host.aspx
I'm having a hardtime to see when I should or would use WCF. Why? Because I put productivity and simplicity on top of my list. Why was the ASMX model so succesful, because it worked, and you get it to work fast. And with VS 2005 and .NET 2.0 wsdl.exe was spitting out pretty nice and compliant services.
In real life you should have very few communication protocols in your architecture. This keeps it simple an maintainable. If you need to acces to legacy systems, write specific adapters for them so they can play along in the nice shiny and beautiful SOA world.
WCF is much more powerful than ASMX and it extends it in several ways. ASMX is limited to only HTTP, whereas WCF can use several protocols for its communication (granted, HTTP is still the way most people will use it, at least for services that need to be interoperable). WCF is also easier to extend. At least, it is possible to extend it in ways that ASMX cannot be extended. "Easy" may be stretching it. =)
The added functionality offered by WCF far outweighs the complexity it adds, in my opinion. I also feel that the programming model is easier. DataContracts are much nicer than having to serialize using XML serialization with public properties for everything, for example. It's also much more declarative in nature, which is also nice.
Wait.... did you ever use .NET Remoting, cause thats the real thing its replacing. .NET Remoting is pretty complicated itself. I find WCF easier and better laid out.
I don't see it mentioned often enough, but you can still implement fairly simple services with WCF, very similar to ASMX services. For example:
[ServiceContract]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class SimpleService
{
[OperationContract]
public string HelloWorld()
{
return "Hello World";
}
}
You still have to register the end point in your web.config, but that's not so bad.
Eliminating the verbosity of the separated data, service, and operation contracts goes a long way toward making WCF more manageable for me.
VS2008 includes the "Add Service Reference" context menu item which will create the proxy for you behind the scenes.
As was mentioned previously, WCF is not intended solely as a replacement for the ASMX web service types, but to provide a consistent, secure and scalable methodology for all interoperable services, whether it is over HTTP, tcp, named pipes or MSMQ transports.
I will confess that I do have other issues with WCF (e.g. re-writing method signatures when exposing a service over basicHTTP - see here, but overall I think it is a definite imrovement
If you're using VS2008 and create a WCF project then you automatically get a test harness when you hit run/debug and you can add a reference without having to use svcutil.
My initial thoughts of WCF were exactly the same! Here are some solutions:
Program your own proxy/client layer utilising generics (see classes ClientBase, Binding). I've found this easy to get working, but hard to perfect.
Use a third party implementation of 1 (SoftwareIsHardwork is my current favourite)
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.
In what scenarios must WCF 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
source: main source of text
MSDN? I usually do pretty well with the Library reference itself, and I usually expect to find valuable articles there.
In terms of what it offers, I think the answer is compatibility. The ASMX services were pretty Microsofty. Not to say that they didn't try to be compatible with other consumers; but the model wasn't made to fit much besides ASP.NET web pages and some other custom Microsoft consumers. Whereas WCF, because of its architecture, allows your service to have very open-standard--based endpoints, e.g. REST, JSON, etc. in addition to the usual SOAP. Other people will probably have a much easier time consuming your WCF service than your ASMX one.
(This is all basically inferred from comparative MSDN reading, so someone who knows more should feel free to correct me.)
WCF should not be thought of as a replacement for ASMX. Judging at how it is positioned and how it is being used internally by Microsoft, it is really a fundamental architecture piece that is used for any type of cross-boundary communication.
I believe that WCF really advances ASMX web services implementation in many ways. First of all it provides a very nice layered object model that helps hide the intrinsic complexity of distributed applications.
Secondly you can have more than request-replay messaging patterns, including asynchronous notifications from server to client (impossible with pure HTTP), and thirdly abstracting away the underlying transport protocol from XML messaging and thus elegantly supporting HTTP, HTTPS, TCP and other. Backward compatibility with "1-st generation" web services is also a plus.
WCF uses XML standard as the internal representation format. This could be perceived as advantage or disadvantage, especially with the growing popularity "fat-free alternatives to XML" like JSON.
The difficult things I find with WCF is managing the configurations for clients and servers, and troubleshooting the not so nice faulted state exceptions.
It would be great if anyone had any shortcuts or tips for those.
I find that is a pain; in that I have .NET at both ends, have the same "contract" dlls loaded at both ends etc. But then I have to mess about with a lot of details like "KnownType" attributes.
WCF also defaults to only letting 1 or 2 clients connect to a service until you change lots of configuration. Changing the config from code is not easy, shipping lots of comfig files is not an option, as it is too hard to merge our changes into any changes a customer may have made at the time of an upgrade (also we don't want customers playing with WCF settings!)
.NET remoting tended to just work most of the time.
I think trying to pretend that .NET to .NET object based communications is the same as sending bit so of Text (xml) to an unknown system, was a step too far.
(The few times we have used WCF to talk to a Java system, we found that the XSD that the java system gave out did not match what XML it wanted anyway, so had to hand-code a lot of the XML mappings.)