ChannelFactory.Close VS IClientChannel.Close

Question

Consider the following code which is typcial of many ChannelFactory examples:

WSHttpBinding myBinding = new WSHttpBinding();
EndpointAddress myEndpoint = new EndpointAddress(
   ConfigurationSettings.AppSettings["HelloWorldServiceURL"]);  

ChannelFactory<IHelloWorldService> myChannelFactory = 
   new ChannelFactory<IHelloWorldService>(myBinding, myEndpoint);

IHelloWorldService proxy = myChannelFactory.CreateChannel();
((IClientChannel)proxy).Open();
HelloWorldDataContract dc = proxy.SayHello();
((IClientChannel)proxy).Close();

Note that when proxy.Open() is called, both the the channel's state and the ChannelFactory's state become "Opened". When proxy.Close() is called, the channel's state becomes "closed", but the ChannelFactory's state remains "Opened".

Should one be closing the ChannelFactory as well? I don't seem to see this in many examples. Also, if possible please explain the difference between having a channel open vs having a channel factory open.

Additionally, I am aware of the IDisposable issue, so it probably can be ignored for the sake of this question unless it has direct impact on the answer.

Solution 1

As you know, the ChannelFactory creates the client channel based on configuration. You may want to create multiple client channels from an existing factory (to the same endpoint as that is locked). If you're done using the factory to create channels, there is no reason not to close it.

But, why might you want to keep it open? Here's an interesting article on WCF clients that says:

Checking the value of the System.ServiceModel.ICommunicationObject.State property is a race condition and is not recommended to determine whether to reuse or close a channel.

Rather than reuse a channel, you might want to simply create a new one with the channel factory. More on the client architecture is here.

Solution 2

I found the main answer inaccurate so I am responding here.

Obviously Microsoft has made an absolute mess out of Channles and Factories and Clients. Documentation is not also helpful since they seem to be there just to cover up the mess so I had to resort to testing.

With the performance issues regarding non-cached Channels, implementation changed in v3.5 to address these and added caching but that only complicated the issue.

The point is channel in ChannelFactory is in fact not different from the channel used by IClientChannel when you create a channel using ChannelFactory.CreateChannel(). It is all the same pot. Believe me not? Try:

ChannelFactory<IService> factory = new ChannelFactory<IService>();
// ...
IService service = factory.CreateChannel();
factory.Close();
service.DoIt() // Throws object disposed exception

So really, internally it is all the same channel. I personally have started disposing the channel factories and not client channels and have not encountered any issue. I have also tried doing this in a loop with creation of 100000 client channels, and only closing ChannelFactory.

Solution 3

Another option is to use the static CreateChannel method: msdn.microsoft.com/en-us/library/aa344556.aspx

Solution 4

The answer is already here, but it is spread over several comments and answers and not entirely clear, hence my answer.

Should one close the ChannelFactory as well as the Channel?

No. If you want to create multiple Channels from each ChannelFactory, you should dispose of the ChannelFactory, which will dispose all the Channels it created for you.

If you want to create one channel for each (endpoint, binding) pair, you should use this static function: ChannelFactory<ServiceType>.CreateChannel(binding, endpoint) (which avoids the issue as it does not create a second IDisposable), and you should dispose of the channel it returns.

Disposing of both the channelfactory and any of the channels it created will raise an ObjectDisposed exception.

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