Sunday, November 14, 2010

WCF 4 - File Less Activation, Default Endpoints and Default Bindings

Started going through WCF 4 a few months back, however, its today I got a chance to write down something about it

So let me talk about something that was really interesting when I first read about it, File Less Activation of services.

In WCF 3.5 when you wanted to host a service in IIS, you had to go through, adding endpoints, bindings and also a SVC file so that IIS can pick the request up.

In WCF 4, this has been simplified so much, that you can get a service up and running in no time.
Lets take an example, I created a service Service1 in a namespace DefaultEndpointSVC, and this is my web.config file....

<add service="DefaultEndpointSVC.Service1" relativeAddress="myService.svc"/>


Now, if I go and deploy my service in IIS inside a virtual directory /DefaultEndpointSVC, I can access my service like this...

Note that I did not add any svc file called myService.svc, instead I have configure it in the serviceActivations element, the relativeAddress attribute specifies the relative .svc file and the service attribute specifies that service to activate when IIS gets a request for a "myService.svc" file and in our case, our Service1 will get activated.

Now, are we missing something here?....where is the endpoint tag? wasn't WCF all about the ABC (address, binding and contract)??

WCF 4 introduces the concept of DefaultEndpoints, that is if you dont configure an endpoint, WCF will add a default endpoint for you..., so now the question how does it do this..

WCF does this by looking at the addressing schema, in our case, we are accessing our service through http, and because we have not defined an endpoint in our config file, it will add a basicHttpBinding endpoint.

WCF has default binding for different transport protocols, for http the defualt binding is basicHttpBinding, for net.tcp it used netTcpBinding; you can get a list of the default bindings that WCF uses from the machine.config.comments.config file found in the folder
C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\Config\ ; within the section protocolMapping

In WCF 4.0, you can put your WCF configurations extensively in the machine.config file, so that it would effect all the services hosted in that machine. So, if all your services use wsHttpBinding, all you have to do is change the default protocol mapping to choose wsHttpBinding instead of the default basicHttpBinding like this...

<add scheme="http" binding="wsHttpBinding" bindingConfiguration="" />

Now, what if, for a new service that you are creating you need to expose it as basicHttpBinding, you put the above line your web or app config, this would override the machine level or the default protocol mapping.

If you have noticed, you would see there is no binding configuration, for each binding there is an associated default binding, if you want to change this at your application level, you just need to add that binding in the config file and you don't need to no longer associate the binding name on the endpoint (see config section below), if you place a netTcpBinding binding configuration, then any net tcp endpoint defined for that application will pick up that binding configuration, but you can still use named configurations for your endpoints.

The advantage of no longer needing to associate your binding configuration into your endpoint is powerful, now you can just add the binding configuration with the standard values for your applications into your machine config like this...

<!-- put your settings here -->

Notice that there is no name attribute, hence this binding configuration will be used in any service that is hosted in this machine that uses net.tcp endpoint but without a named binding.

The same concept is there for service behaviors, hence you can put a default service behavior again in your machine config file that can be globally used in all the services hosted.

You can also name this behavior and now if you specify the same behavior name in your application web.config, the settings for the behavior in the machine.config will be inherited.

Guess, that all I have time for now...need to go and finish up the movie I stared...

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