If on the other hand, you are running the application on a virtual site in IIS which supports multiple host headers (let’s say: foo.bar.com and www.foo.bar.com) you’re likely to run into an exception like the following.

[ArgumentException: This collection already contains an address with scheme http. There can be at most one address per scheme in this collection.
Parameter name: item]
   System.ServiceModel.UriSchemeKeyedCollection.InsertItem(Int32 index, Uri item) +11520590
   System.Collections.Generic.SynchronizedCollection`1.Add(T item) +67
   System.ServiceModel.UriSchemeKeyedCollection..ctor(Uri[] addresses) +49
   System.ServiceModel.ServiceHost..ctor(Type serviceType, Uri[] baseAddresses) +129
   System.ServiceModel.Activation.ServiceHostFactory.CreateServiceHost(Type serviceType, Uri[] baseAddresses) +28
   System.ServiceModel.Activation.ServiceHostFactory.CreateServiceHost(String constructorString, Uri[] baseAddresses) +331
   System.ServiceModel.HostingManager.CreateService(String normalizedVirtualPath) +11659932
   System.ServiceModel.HostingManager.ActivateService(String normalizedVirtualPath) +42
   System.ServiceModel.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath) +479

This indicates that a binding address which starts with http is already in use, when trying to automatically add the second address. The solution to this is as simple as updating your Web.Config file like shown here. Please take a look at line #9:

<configuration>
    <!-- ... -->
    <system.serviceModel>
        <behaviors>
            <!-- ... -->
        </behaviors>
        <serviceHostingEnvironment aspNetCompatibilityEnabled="true">
            <baseAddressPrefixFilters>
                <add prefix="http://foo.bar.com" />
            </baseAddressPrefixFilters>
        </serviceHostingEnvironment>
        <services>
            <!-- ... -->
        </services>
        <bindings>
            <!-- ... -->
        </bindings>
    </system.serviceModel>
</configuration>

Addendum from Feb 6: Apparently I was not entirely correct about using the service on a site with multiple host headers. While the above changes to Web.config fix the initial problem, they introduce a new problem. You’ll realize that this will work only for the requests using one of the host headers. The request to the service using the other host headers will throw a 404. This is a reported bug and will hopefully be fixed soon.

The post Fun with JSON and WCF appeared first on Tales of a Code Monkey.