We're trying to use Dependency Injection for a WCF Service. The Service has a dependency on a Unity Container. The container is used to find the appropriate class that implements an IJob Interface (based on a JobKey parameter in the method call) and calls a method on it.
The Service is being hosted in MVC2. I've omitted as much irrelevant stuff as possible from the snippets below. Full code available if required...
What I've done so far:
Based on this MSDN Article, I've created a custom InstanceProvider which should instantiate my service and pass it a container.
I then created a very noddy ServiceBehavior to use the InstanceProvider and finally a BehaviorExtension which just returns the ServiceBehavior.
Public Class WCFDIInstanceProvider
Implements IInstanceProvider
Private ServiceType As Type
Private Property _Container As IUnityContainer
Private ReadOnly Property Container As IUnityContainer
Get
If _Container Is Nothing Then
_Container = InitialiseContainer()
End If
Return _Container
End Get
End Property
Public Sub New(ByVal ServiceType As Type)
Me.ServiceType = ServiceType
End Sub
Private Function InitialiseContainer() As IUnityContainer
'Code which scans assemblies and populates the container as appropriate
'I'm confident this code works as I've tested it elsewhere
Return Container
End Function
Public Function GetInstance(ByVal instanceContext As System.ServiceModel.InstanceContext) As Object Implements System.ServiceModel.Dispatcher.IInstanceProvider.GetInstance
Return GetInstance(instanceContext, Nothing)
End Function
Public Function GetInstance(ByVal instanceContext As System.ServiceModel.InstanceContext, ByVal message As System.ServiceModel.Channels.Message) As Object Implements System.ServiceModel.Dispatcher.IInstanceProvider.GetInstance
Return Container.Resolve(Me.ServiceType)
End Function
End Class
And the ServiceBehavior:
Public Class WCFDIServiceBehavior
Implements IServiceBehavior
Public Sub ApplyDispatchBehavior(ByVal serviceDescription As System.ServiceModel.Description.ServiceDescription, ByVal serviceHostBase As System.ServiceModel.ServiceHostBase) Implements System.ServiceModel.Description.IServiceBehavior.ApplyDispatchBehavior
For Each ChannelDispatcherBase As ChannelDispatcherBase In serviceHostBase.ChannelDispatchers
Dim ChannelDispatcher As ChannelDispatcher = TryCast(ChannelDispatcherBase, ChannelDispatcher)
If ChannelDispatcher IsNot Nothing Then
For Each Dispatcher As EndpointDispatcher In ChannelDispatcher.Endpoints
Dispatcher.DispatchRuntime.InstanceProvider = New WCFDIInstanceProvider(serviceDescription.ServiceType)
Next
End If
Next
End Sub
And finally, the really noddy BehaviorExtension:
Public Class WCFDIBehaviorExtension
Inherits BehaviorExtensionElement
Public Overrides ReadOnly Property BehaviorType As System.Type
Get
Return GetType(WCFDIServiceBehavior)
End Get
End Property
Protected Overrides Function CreateBehavior() As Object
Return New WCFDIServiceBehavior
End Function
End Class
The WCF Config tool seems to like all of the above and has generated the following Config XML:
<serviceHostingEnvironment multipleSiteBindingsEnabled="true"
aspNetCompatibilityEnabled="true">
<serviceActivations>
<add relativeAddress="WebJob.svc"
service="MyApplication.WebJobService"
factory="System.ServiceModel.Activation.ServiceHostFactory" />
</serviceActivations>
</serviceHostingEnvironment>
<standardEndpoints>
<mexEndpoint>
<standardEndpoint name="WebJobServiceMex" />
</mexEndpoint>
</standardEndpoints>
<behaviors>
<serviceBehaviors>
<behavior name="WCFDIServiceBehavior">
<serviceMetadata httpGetEnabled="true" />
<serviceDebug includeExceptionDetailInFaults="true" />
<WCFDIBehavior />
</behavior>
</serviceBehaviors>
</behaviors>
<services>
<service name="WebJobService">
<endpoint address="" binding="basicHttpBinding" bindingConfiguration="httpBinding"
name="HTTPEndpoint" contract="MyApplication.JobService.Common.IWebJobService" />
<endpoint binding="mexTcpBinding" bindingConfiguration="" name="mexEndpoint" />
</service>
</services>
The exception I get is:
System.ServiceModel.ServiceActivationException: The service '/MyAppDir/WebJob.svc' cannot be activated due to an exception during compilation. The exception message is: The service type provided could not be loaded as a service because it does not have a default (parameter-less) constructor. To fix the problem, add a default constructor to the type, or pass an instance of the type to the host.
System.InvalidOperationException: The service type provided could not be loaded as a service because it does not have a default (parameter-less) constructor. To fix the problem, add a default constructor to the type, or pass an instance of the type to the host.
WebHost failed to process a request.
Sender Information: System.ServiceModel.ServiceHostingEnvironment+HostingManager/13982700
Exception: System.ServiceModel.ServiceActivationException: The service '/MyAppDir/WebJob.svc' cannot be activated due to an exception during compilation. The exception message is: The service type provided could not be loaded as a service because it does not have a default (parameter-less) constructor. To fix the problem, add a default constructor to the type, or pass an instance of the type to the host.. ---> System.InvalidOperationException: The service type provided could not be loaded as a service because it does not have a default (parameter-less) constructor. To fix the problem, add a default constructor to the type, or pass an instance of the type to the host.
at System.ServiceModel.Dispatcher.InstanceBehavior..ctor(DispatchRuntime dispatch, ImmutableDispatchRuntime immutableRuntime)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime..ctor(DispatchRuntime dispatch)
at System.ServiceModel.Dispatcher.DispatchRuntime.GetRuntimeCore()
at System.ServiceModel.Dispatcher.ChannelDispatcher.OnOpened()
at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)
at System.ServiceModel.ServiceHostBase.OnOpen(TimeSpan timeout)
[Blah]
Process Name: w3wp
Process ID: 2108
Which makes sense assuming it's not applying my custom ServiceBehavior - The default ServiceBehavior's InstaceProvider can't instantiate the service.
Some things to note: If I add a parameterless constructor to my service, I don't get an exception (but of course, I don't get passed a container either) so I'm fairly confident I've found the source of the problem
Can someone please point out what I'm doing wrong?
