Silverlight polling duplex configuration error

Question

I have the following in my web.config file under system.serviceModel:

<extensions>
<bindingExtensions>
  <add name="pollingDuplex" type="System.ServiceModel.Configuration.PollingDuplexHttpBindingCollectionElement, System.ServiceModel.PollingDuplex, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
</bindingExtensions>
</extensions>

And what I get when I try to access a service in the browser is the error message:

Parser Error Message: An extension of type 'System.ServiceModel.Configuration.PollingDuplexElement, System.ServiceModel.PollingDuplex, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' already appears in extension collection. Extension types must be unique.

So it seems the PollingDuplexElement has already been registered in the extension collection. I just can't figure out where, or under what name.

I've tried looking through the machine.config file, not finding any references to the polling duplex assembly. There is also no other reference to the assembly in my web.config file, and Google has not been of much help.

Any ideas would be much appreciated :)

Answer 1

There was an old web.config file located on my IIS root that also added the extension. Deleted it, and now it works fine.