WCF instance per channel

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I am self-hosting WCF services and have a special(?) requirement: I need a service instance for each channel. I need some advice on how to do this.

I have surmised that I cannot use InstanceContextMode.PerSession since I want each channel to have its own service instance, not just per session. I cannot user PerCall since I want the same instance for a given channel. Therefore, it appears that I need to use Single, but with some special handling. Does this sound correct? Or, is there a way to satisfy my requirement with a combination of InstanceContextMode, SessionMode, etc.?

After some reading, it appears that my special handling needs to be in a custom IInstanceProvider. Does this sound correct? Is there something else I need to do?

I am feeling my way around a bit and just looking for advice on whether I am on the right path. If not, please point me in another direction and I'll check it out. If so, then any helpful advice (articles, examples) is most welcome.

Posted 30-May-13 6:27am

kalkwarf

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**Zoltán Zörgő** · Answer 1 · 2013-05-30T08:13:00

Solution 1

One single question: why do you need that? Instantiation has some other aspects in mind (this is a good comparison: Three ways to do WCF instance management[^]). If you want something like per-channel, make the logic common, but create several different singleton services each bound[^] to that channel/protocol.

Posted 30-May-13 8:13am

Zoltán Zörgő

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kalkwarf 30-May-13 15:26pm

Yes, I read that article. I understand the basics. However, none of the three options fits my needs.

On the server, I have multiple pieces of hardware each with the same interface. Some of the pieces are identical or ultimately use the same class for communication. Therefore, I need to indicate for which I need a separate instance of that class. The logical method seems to be a channel.

Zoltán Zörgő 30-May-13 15:41pm

The channel concept is not related to the method. It is a matter of communication, like the tcp/ip stack. See: http://debugmode.net/2011/10/15/what-is-channel-in-wcf/
As I know, there is no way to make binding per method. You can however make multiple endpoints/bindings for the same service: http://msdn.microsoft.com/en-us/library/ms751515.aspx

kalkwarf 30-May-13 16:10pm

Thanks for the Channel article.

So, there is no way to indicate that I want separate service instances within a single session?

I had contemplated creating separate endpoints for each piece of hardware, but that seemed to be a waste since I would have to create separate ServiceHost instances for each. However, I may have to do this.

kalkwarf · Answer 2 · 2013-06-03T07:43:00

I came up with a solution.

- I created a custom ServiceHost and InstanceProvider.

- I added multiple endpoints to my ServiceHost. For some reason I thought that a ServiceHost could only handle one endpoint. Not true, you can add many. This allowed me to handle all requests for a particular service in one place (my custom host).

- Remember that I wanted to create separate service instances per channel. Channel information can be found in the OperationContext.Current.Channel object. There are several properties one can use to distinguish one channel from another.

- In my custom InstanceProvider.GetInstance I create a service instance for each unique URI. I track them with a Dictionary. If I have already created an instance for a given URI, I simply return the one I already created.