I am developing one windows phone app. I have created one WCF application. I have added Service Reference. I want to disable asynchronous operations in it's configuration. By default it show's me enable.
How can I disable Allow generation of asynchronous operations?
Since Silverlight/WP doesn't allow synchronous calls to WCF services, only generation of asynchronous operations is available.
Related
Is it possible and allowable for MFP application to call web services directly without using adapters?
Yes. It's called making standard AJAX calls. Which means these calls will not benefit the features that are possible through MobileFirst (such as security, etc).
I have to developed one application:-
Which will have two part ADMIN and Clients
Components of application:-
1) WCF Services:-To capture the screen's images of all clients machine through some sort of UI (say button "Capture")
2) Clients: - This will be any exe run on different machine and consuming WCF services.
So as per architecture:-
1) All clients .exe will subscribe to WCF service, so that the channel is established between client and service
Using this channel service should enable callback (instruct) to all clients (.exe on different machine) to capture the desktops image
And save it in some particular location.
Thing I know:-
1) This can be achieved with Callback mechanism in wcf.
Things I am looking for:-
How and where to generate the event so that all clients are instructed to capture desktop image.i.e how to use wcf service in some sort of UI (say button)"Capture”. When admin click on capture button the event should raise to all the clients to capture the screen.
Please help how to perform this task with WCF callback
Actually, you have given the answer yourself already. The admin needs to use a UI to trigger the event. So this UI is yet another client for the WCF service. Your service needs to be configured as InstanceContextMode.Single in order to have only one instance with the shared state (i.e. the list of registered clients). You will have to think about concurrency as well when you have shared state.
The button in the admin UI can then trigger a method in the same WCF service that will use the callbacks to notify the clients.
I have a good understanding SignalR Hubs in a client/server scenario, where both the client and server are tightly coupled.
Let's say I have a WCF service that receives an update from some external resource. That service could update the database with a new value. However the client would need to be notified that an update has occurred. This could be handled through a service proxy that notifies the client (sounds a bit like polling) or some cache resource.
I could create C#-based clients and connect all the nodes via SignalR hubs, but this creates a closed, non-distributed system.
A SignaR hub that attaches to a WCF service could use the .Net 4.5 could implement a WCF asynchronous service operation, where a hub client would be notified with any service data changes.
I saw something similar in Push Notifications with NServiceBus and SignaR, but not sure if this is an optimal production-level solution.
What other methods could be used in this scenario and how would they be implemented?
If you are not using push notifications directly to the client or some kind of long polling then it is pretty typical to communicate with clients on another channel altogether. Not knowing the business case, it is hard to tell what would be feasible. Usually this manifests itself in the form of SMS, push notifications to mobile, email, etc. This does not answer your question directly, but you may find that there is another way to achieve your goal.
So I'm looking into implementing NServiceBus in our current setup and just trying to get a better understanding of how things should be setup.
Our current setup consists of multiple clients (websites, scheduled tasks, etc..) calling a WCF service we have set up for handling the sending of emails. Of course, if the service goes down then our clients start getting errors and all of those messages are then lost (one of the reasons we want an ESB).
I've seen how you can configure your WCF service to handle nservicebus messages in a pub/sub setup. What I'm not sure on is what is the best way to set it up.
Setup 1:
Client (Publisher) -> NServiceBus handler (Subscriber) -> WCF Service
In this case, to scale you'd increase the number of handlers (hosted nservicebus services?), keeping just the one WCF service.
Setup 2:
Client (Publisher) -> WCF Service (Subscriber)
This one you just increase the number of WCF services to scale (updates would be a nightmare).
I just started looking into the ESB architecture in general so if I'm completely off let me know. I'm essentially just wanting to know what is working for you, and what the "best practice" tends to be.
Thanks!
I'm not completely clear on what you need WCF for anymore if you implement this via NServiceBus. Is the WCF component required for anything besides receiving messages (to send an email) from the multiple clients? If not, you could remove WCF from the equation.
From the sound of it, you will also want the Service to act as a single logical endpoint that handle requests to send emails. If that's the case, you will want to use Send (a command) instead of Publish (an event). Publish is used to broadcast an event, which means that something happened already; Send is used to instruct another component to do something. It sounds like you want the latter.
Scaling of an endpoint can be done via the Distributor. This may or may not be useful depending on where you expect the bottleneck to be.
Edit: Based on your comment, I would simply go with the second setup, and just add the handler to the WCF service. If you are hosting WCF in IIS, make sure you have something that wakes the process up if the app pool recycles (the incoming message won't wake it up the same way an incoming request to WCF will).
We do something similar internally where one NSB endpoint handles all the sending of email. The clients can either use NSB directly to Bus.Send() the command to send a message to the email endpoint or you can expose that endpoint via WCF as well (only to get the commands over to the endpoint). Once the endpoint has the commands, they would just call your existing service to maintain compatibility with your existing clients.
While making my first ajax attempts, I decided also, to go to use IIS hosted WCF now. The strange thing is, that the WCF cannot process several requests parallel for the same user/session, if sessionmode is enabled! If sessionmode is disabled on asp.net, the requests are processed parallel. The broser/client may execute several different requests, where some of them are long running. This blocks all further requets and make my ajax app unusable.
This applies to asmx [webservices] also. I had a big hope, to compile the webservice methods using "IReadOnlySessionState" interface, but this has - in oppsite to webpages - no influence. But I need access [most times readonly] to the asp.net session!
Does someone knows any solution to this problems.
Anyway, thanks a lot!
br--mabra
In .NET 4, you can do this in Application_BeginRequest
if (Context.Request.Path.EndsWith("xxx.svc"))
Context.SetSessionStateBehavior(SessionStateBehavior.ReadOnly);
I found this:
http://blogs.msdn.com/silverlightws/archive/2009/09/30/having-a-pollingduplex-service-and-any-other-wcf-service-in-the-same-website-causes-silverlight-calls-to-be-slow.aspx
Which states,
"All WCF services require read/write session state access if you enable ASP.Net sessions, which causes the replies to be queued sequentially. Ideally user should be able configure the WCF handler to be read only, which would allow polling duplex services to work with sessions. Unfortunately this is unsupported at this point."
...the only thing I can think of is if there's some way to manually force early release of the lock. I'm looking into that now.
You can provide a custom session state provider
See: http://koolsand.blogspot.com/2010/02/why-iis-hosted-wcf-services-does-not.html
whenever a request contains svc in the
path it intimates default session
state provider to use readonly lock
and not read-write lock. So using
readonly lock will allow the next wcf
call to be executed concurrently.