I am migrating a web service to WCF so I can use binary encoding. I am now realizing that the session calls and application state calls are not recognized. WCF is supposed to be better then a web service so I am assuming that there is a better way to do things.
1) How do I maintain session and call a web service that uses session?
2) How do I replace the application object?
For those of you who are migrating a large project and cannot afford to be so ideological, I found a real answer here:
http://megakemp.wordpress.com/2008/11/27/migrating-aspnet-web-services-to-wcf/
In WCF, the best practice is not to have any state whenever possible, since your clients should be calling you with a "per-call" approach - each call from a client gets a new instance of your WCF service class, which is totally independent of anything else, ideally.
If you need to have persistent state, store it in a persistent store - typically a database.
WCF is also by default totally independent of ASP.NET and IIS, and thus cannot leverage the HttpContext, HttpSessionState and so forth objects - since it might be self-hosted in a console app which has no knowledge of IIS, HTTP context etc.
The question is: what exactly do you really use from those HttpSessionState and HttpApplicationState objects? Somehow, you need to abstract that away or solve it some other way, e.g. have the client send you that information (as a parameter on your web service method call, or as a header in the message), or have the client send you a "token" of sorts which allows you to retrieve the relevant info from e.g. a database table.
Chapter 4 in Juval Lowy's excellent Programming WCF Services (link) is all about Instance Management. There are sections on Per-Session services and Durable services, each of which might be what you're looking for.
However, Marc's point is very valid. There are a lot of cons to using session with WCF services, but it is possible. Lowy discusses a lot of this in some detail.
Related
So bear with me, i am new at MVC and WCF. I already have a set of services (WCF) that exposes my BLL and I am trying to consume those from my MVC.net web application but i am unsure on how to perform security operations here.
These are my app requirements:
Be able to consume WCF services using different credentials for every user on the web application
My BLL (WCF) needs to know what consumer is calling it (right now I only have the MVC app but i am planning to add iOS and Andriod calls to it, so later on i will add REST services to the WCF endpoints) Is there any design pattern for this out there? (or should i just use the soap header to include the caller ID? should i use some sort of caller secret or something?)
I need a security mechanism like Tokens or something so I dont have to pass the username and password on every call of the service method (WCF)
What i have so far:
WCF uses a certificate and and with a custom username validator.
I have manually coded proxies using the contract interfaces instead of generated proxies: But I hate the fact that i have to validate username and password every time a call is made to a WCF service. How in heaven can i use Tokens here? like to know if a given token sent on the soap header is valid or not yet expired? i have searched a lot and no tutorial/code/example is clear enough for me to actually start coding that ;(
I am trying to cache the ChannelFactory but should I? i mean, i will need to cache a channer factory per logged in user per contract ;( is that ok? what can i do here?
Thanks in advance!
Should you cache the ChannelFactory per user per contract?
It depends. There are a couple of considerations. Instantiating a channel factory could take up to 70ms. If you are doing this repeatedly, you will see a noticeable performance hit if you are not caching the ChannelFactory and instantiating one (or more) each time a user makes a http request to your MVC app that results in controller actions calling web services. This would indicate that caching the channelFactory would be beneficial for speed.
On the other hand, depending on the number of users you have, if you are caching a lot of channel factories (in a static dictionary for example), you are going to start to use a non-trivial amount of memory - this may become an issue for you.
You have to decide if the cost of instantiating channel factories on the fly (and correctly closing / aborting them and their contained channels) is too high a price vs increasing memory utilisation in the application pool hosting your MVC app.
Either way, I strongly advise to profile your app before you deploy to production.
What is the difference between WCF Services and Web Services in .netWhen should I use WCF and when to use Web Services.Is REST and WCF service the same? Thanks
Web Service is an abstract term encompassing a large variety of data providers for distributed systems. Perhaps you are referring to ASMX web services, which can still be found in the wild but aren't really widely used in new development these days.
WCF Service is Microsoft's implementation of SOAP. There are others implementations or you could roll your own (not recommended).
SOAP is a kind of stateful, session-based, message-based web service. It's good if your service is designed as a set of complex actions.
REST is a stateless, sessionless, resource-based web service. It's good if your service is designed to access data and perform simple CRUD operations on it. SOAP and REST are mutually exclusive. A service cannot be both. There are ways to manipulate vanilla WCF to make is RESTful but these techniques are becoming deprecated. If you want to implement a RESTful web service there are two main choices in the Microsoft world: WCF Data Services and ASP.NET Web API.
REST is an architecture
WCF is a API in .NET Framework to build connected service oriented application.
In olden days a functionality developed as Web Service was accessible via internet and the same to be available on local network was available via Remoting.
Using WCF we don't need to develop different code for it to be accessible over internet and on local network. Just configuring it with bindings would be enough.
That is a very wide question...I am going to just give a brief high-level answer and suggest that you do some more searching as there are is already a lot written on each subject. But, hopefully this should give you a push in the right direction.
First, typically when people refer to WCF Services and Web Services, they are referring to the newer WCF conventions that make service calls fairly generic (they can be SOAP, REST, etc) and the old .asmx SOAP method of Web Services. So, along these lines, I would suggest looking more into WCF and SOAP/.ASMX for the difference of WCF and older Web Services.
As to WCF and REST, they are not the same. REST is more of an architecture, whereas WCF is a framework. As I already mentioned, WCF can be used to make SOAP calls or REST calls. I am not sure I can add much more without going into greater detail.
I will see if I can find some good articles on REST and WCF a little later, though. Personally, I do not see a reason to even pursue very far into the older way of calling web services (.ASMX pages) as WCF has pretty much made that obsolete. However, learning many different ways to skin a cat can be useful in an endeavor to find what fits you best.
Again, this is VERY high level, but these are very general topics with a lot surrounding each, so hopefully a high level overview will help direct you in studying deeper on each subject.
Some people mean "ASMX" when they say "Web Services".
Others just use "Web Services" to mean the generic technology, and consider WCF to be the current way to create Web Services on the .NET platform. The other kind are "ASMX Web Services", as distinguished from "WCF Web Services".
The "other kind" are a legacy technology, supported only for backwards compatibility. They should not be used for new development, so there's no point in you learning about them.
As others have stated, "REST" is an architecture style, not a technology.
WCF is multifaceted, so I'm going to speak of it with respect to its most common usage. The general difference between WCF and REST services is centered around the content. A REST call is usually more message/document/entity centered (With customer entities, find those starting with M; With order entities, get order 12 and is tied to the HTTP protocol. WCF tends to be more operation centered (Invoke find operation with params, Invoke get operation with parameters). WCF also isn't tied to HTTP.
FYI, there are extensions to create REST based services using WCF (WebInvoke, WebGet attributes).
Wcf:wcf is a technology as part of .net framework which provides environment to work with different distributed technologies an by following unified programming model.
wcf create a proxy.
wcf support data contract serializer.
records shown xml format.
**Rest:**Rest is an architectural style.which says use the existing features of the web in more effective,efficiency and simple manner.verbs like insert,update and delete.
Rest cannot create a proxy.
rest records shown jason format.
Web Service:a service which is hosted on website is called as webservice.
web service support xmlserializer
I see this is quite an old thread, but I have asked a similar question recently.
The answers given have all similar relevance, but in my opinion Ray was the closest to what was actually asked.
When designing or refactoring a web based solution, you always get the question should we go with SOAP or REST. The answer lies in the complexity of the business logic required behind the service. REST is good for simplistic API calls that usually contains small sets of requested data or over night processing with large sets, but mainly for data requests. SOAP is more of an interactive day to day service with business logic as well. For example many methods with plenty of parameters.
What we do as part of our web based solution, is to try and make use of both. For internal methods and primary functionalities we use SOAP, but for exposed APIs we prefer REST.
Framework related, definitely WCF as preferred choice, irrespective if SOAP or REST.
I have just started evaluating whether or not I should be using OData influenced wcf data services or a standard WCF service application as the primary data source for Silverlight applications. I would like your thoughts on which is a better way under what situation/circumstance. What is lighter over the wire, easier to maintain, etc.
What I have gathered so far is:
There are no Wcf data service templates in VS2010 that I know of, and I will need to create a asp.net web project first and then add a wcf data service, so its going to affect how I structure my projects.
WCF Data services expose actual table names over the service. I don't know yet of a way I can alias them and I'm not sure its a good idea to let the world know my table structure
In a standard wcf service I will need to write linq queries against the EF or Domain service classes on the service side, while in a data service I can move that processing logic to the client.
At first glance examining the classes exposed by the wcf data services seem easier to read and understand than those exposed by the EF
Do add your thoughts on this..
Thanks for your time.
There are no Wcf data service
templates in VS2010 that I know of,
Not project template - just an item template (for use inside an ASP.NET web site or web app). WCF DataServices are very tightly coupled to HTTP, so they only make sense in a web site/app.
WCF Data services expose actual table
names over the service.
NO ! At least not necessarily. The whole point of EF is that you can decouple the actual physical structure of your database from the (conceptual) model that gets exposed. You can totally rename entities, you can map several entities onto a single table, split up an entity over several tables, you can leave out attributes - anything you like!
At first glance examining the classes
exposed by the wcf data services seem
easier to read and understand than
those exposed by the EF
I doubt it - because by default, WCF Data Services will use a Linq-to-SQL or EF model as their basis, really. You can make that as simple or as complicated as you like.
Using a "regular" WCF service allows you to use the netTcpBinding for much faster performance (thanks to binary message encoding vs. textual messages for other bindings), when using your Silverlight 4 app in a company-internal network (doesn't work for internet scenarios) - not something you can do with WCF DataServices.
The main difference in my opinion is the SOAP vs. REST difference:
SOAP (traditional WCF) is oriented towards methods - you think and design your system in terms of methods - things you can do (GetCustomer, SaveOrder etc.)
REST (the WCF DataServices approach) is all about resources, e.g. you have your resources and collections of resources (e.g. Customers) and you expose those out to the world, with standard HTTP verbs (GET, POST, PUT, DELETE) instead of separate specific methods that you define
So both approaches have their pros and cons. I guess the most important question is: what kind of app are you creating, and what kind of user audience are you targetting?
Update:
for intranet / internal apps, I would think the advantage of a netTcpBinding (binary encoding) would justify using a classic WCF service - also for data-intensive apps, I personally find a method-based approach (GetCustomer, SaveCustomer) to be easier to use and understand
for a public-facing app, using HTTP and being as interoperable as possible is probably your major concern, so in that scenario, I'd probably favor the WCF Data Service - easy to use, easy to understand URLs for the user
There a lot of different ways a Silverlight application can connect back to it’ server. Including
WCF - Windows Communication Foundation
REST (see also)
ADO.NET Data Services (or is this just REST?)
POX - Plain Old XML (E.g basic xml)
RIA services
For each of these please say what it’s for and when you would or wouldn’t use it. I am not looking for a great level of details just a set of “rules of thumb” for choosing between them.
(The problem is when designing your first Silverlight application knowing what to use when you don’t have time to learn all of them.)
If I was to replace Silverlight with WPF in this question what effect would it have on your answers? (I am assuming with WPF that due to firewalls and admin policies a direct connect to the database is not an option.)
My two (euro) cents:
WCF seems best suited when the service can be viewed as the business layer of the application, that is, when your service has "intelligent" operations like "CalculateDiscountForClient".
ADO.NET Data Services (indeed, just a REST implementation) seems appropriate when your application is basically data-centric and the service is simply a front-end for the database. That is, all your service methods are of type GetCustomers, CreateInvoice, etc.
RIA services is a very new technology that I haven't experimented with yet, but it seems to be useful to create applications in which the Silverlight part and the service are very tightly coupled: you define your service classes and methods in the service project, and they are automatically replicated to the Silverlight project in design time. Also, you can define both WCF-style "action" methods and ADO.NET Data Services-style "data" methods. Looks promising.
Use POX if there is a chance that you change the client part from Silverlight to any other technology (for example HTML+AJAX) in the future, since it is the most interoperable option.
About differences for WPF, the only I can think of, is that for data access, whenever possible I would use direct ADO.NET data connections (properly embedded in a data access layer, LINQ to SQL or the like) instead of ADO.NET Data Services, since it is way more flexible. I must say anyway that I have never developed anything in WPF.
We use RIA, and that's the only one of the options that I know, but I do know it, so here's some of my thoughts.
RIA isn't finished yet. It is being worked on. If you are planning to be finished soon, and you're worried about having to support something that has a potential to change quite a bit, then you might want to consider other options. If this is a new project, and you're going to be supporting it for a long time, RIA will probably get easier to use.
Having said that, I kind of think that there won't be many changes in the way the July Preview of RIA works and the way that a finished version will work. Also the level of support seems to suggest that this will become "The Way" to talk to a server in Silverlight.
Just cause it's worth mentioning, have some links:
http://blogs.msdn.com/brada/ Brad Abrams has an example that he is continually updating.
http://forums.silverlight.net/forums/53.aspx this is where you go to ask questions.
http://www.riaservicesblog.com/Blog/ Colin Blair knows his stuff, and he is very helpful.
I think I would not go POX ever again. If you write WCF so that the service itself is independent of the binding and binding is done in configuration files, then WCF is pretty much agnostic about transport and protocol. It can do SOAP, JSON, REST, or its own form of binary serialization. All of this is in the binding. Internally, WCF only specifies what gets exposed in terms of operation and data contracts (all defined by class, method, and property attributes). WCF gives you tremendous flexibility in this regard, with more to come in 2010.
From the Silverlight side, WCF requires that you write some plumbing code. The .NET frameowrk has the tools to build the proxy in your Silverlight project, but you must be prepared to handle all WCF responses asynchronously, and the proxy cannot catch exceptions thrown by the service.
.NET RIA Services hides all this. It uses WCF under the covers, but that is completely hidden. You don't have to write asynchronous code. You define validation once, mostly declaratively, and it works both server-side and client-side. Release 1 will be targeted for Silverlight, so you don't get the versatility to use the service elsewhere. That scope is supposed to be broadened in later releases.
I don't know enough about ADO.NET Data Services to compare. I suspect the answer would depend on whether you want to expose your data to more than just Silverlight usage.
.NET RIA Services looks like the direction I'd want to go (looking at these issues myself, with a large application in mind). The big issues for me will be implementing a very large collection of functionality in the service layer, and not being able to code directly to the data access layer (we have to be able to run on either SQL Server or Oracle).
Using WPF instead of Silverlight changes everything, depending on where your data resides. It's like the old question of Winforms vs. ASP.NET. With WPF, you're building a Windows client app, and you don't need to use any form of service-based data interface at all, unless your data access forces you into it. You'll still want to separate data and business from presentation code, using MVVM, MVC, or MVP. Other than that, you have the option to treat data access as a layer, rather than a wholy independent tier.
WCF is Microsoft's standard for service communication. I would strongly advise anyone to create a service layer using WCF Web APIs (uses WCF, but tailored specifically for REST), which is coming out this April 2012. WCF Web APIs is currently in preview mode.
Remember these rules of thumb:
- your UI will change faster than your service layer. RESTful services will be around in several years, Silverlight probably won't
- will your services ever be APIs? Well...WCF REST is the way to go
- will you mix JavaScript and Silverlight code? WCF REST will make your life easier
- will you have a mobile component (since Silverlight won't run on iOS or android)...REST is preferred.
Don't tailor to the technology, but the app as a whole.
If you want to create a Silverlight Application and you do not care about other clients, then I would choose RIA Services. It is quite painless to use and you do not need to worry how the connection from the client is made (i.e. no client side configuration necessary). RIA also generates classes for all your entities on the client and you can even share your own "server" code with the client if required (useful for enumerations or extension methods).
Remarks:
I never tried this, but if you really need you can access the RIA Service also with other clients, after all RIA Services are built on top of WCF services.
I do not quite understand Akash Kava's security concerns. You can (and have to) control security on the server-side as you would do with any other service.
I have been working on splitting up the app tier and web tier of a web application. In the app tier, I managed to separate the business logic into a bunch of services exposed using WCF proxies. The problem is that these services talk to another legacy application that uses a large CLR object as its primary means of communication. To keep things quick, I had been keeping a copy of this object in the session after I created it the first time. Now I know that WCF can do sessions, but the session storage is per service whereas my business logic is now split into multiple services (as it should be).
Now the questions:
Is there a way to share session storage between WCF services hosted on the same host?
Is this even something I should be doing?
If not, then what are the best practices here?
This is probably not the first time somebody’s had a large business object on the server. Unfortunately for me, I really do need to cache this object per user (hence the session).
It’s possible the answer is obvious and I'm just not seeing it. Help please!
I think instance context sharing can help
http://msdn.microsoft.com/en-us/library/aa354514.aspx
As far as I understand WCF, it is designed to be as stateless as it could be. In a session you can remember some values in your service, but objects are not meant to live outside the scope of a session.
Therefore, I'd think you are in trouble.
Of course, there might be some way to store and exchange objects between sessions that I don't know (I use WCF, but I don't know very much about it, apart from what I need for myself).
(if there is a way to share objects between services, it probably would only work on services you host yourself. IIS hosting might recycle your service sometimes)
Perhaps you can wrap this object in a singleton service. This is a service with only one instance, which will not be destroyed between calls. Because you need an object for each user, this service has to manage a list of them and the calling services has to provide the needed authentication data (or sessionid). Don't forget a timeout to get rid of unneeded objects...
Create a facade service which hosts the large CLR object on behalf of the other app tier services. It can work as an adapter, allowing more specific session identifiers to the more advanced app tier services you have created. The facade can provide a session identifier, like a GUID, which your app tier services can use to get re-connected with the large CLR object.
This provides a few advantages:
Some of your app tier might not need to know about the CLR object at all. They only communicate with the remote facade.
the 'large CLR object' host retains the session object on behalf of the other services who can now share it.
The app tiers now have a facade through which they talk to the legacy service. As you work to refactor this legacy service, the app tier doesn't have to change.
Depending on your setup, you may be able to host the facade via in proc hosting which will give retain performance boost you are seeking.
Breaking things up into subservices seems like a good idea if you want to be able to spread the app out over a farm. However, it's important to keep in mind that whenever an object crosses the appdomain boundary at the vary least it will have to be copied in memory.
It all depends on how big the object is and what kind of data it holds.
If you don't want to pass the object because it's too large you may want to make a query API for the service which receives it. In this way you could manipulate that object without having to do expensive serialization or remoting.
Keep it simple. Since you already have access to Session in your WCF, you can use the SessionID from there. Now:
Create a static dictionary somewhere, where the Key is your sessionId and the value is the business object you want to store.
Instead of accessing the business object in session, just access the sessionid and get the business object from the Value of your dictionary.
(You can also use some type of caching if you wish, for example System.Web.Caching, that way you don't have to cleanup the dictionary manually)