WCF with Ninject throwing ArgumentNullException

Question

I am new to Ninject and trying to evaluate how well it compares to Windsor Castle, which I am more familiar with. My application is a WCF service application hosted in IIS. As a result, I am trying to spin-up the container/kernel and use the NinjectServiceHostFactory to create my service class, etc. Unfortunately, I'm getting an ArgumentNullException instead.

Here's the exception information:

System.ArgumentNullException
Cannot be null. Parameter name: root

   at Ninject.ResolutionExtensions.GetResolutionIterator(IResolutionRoot root, Type service, Func`2 constraint, IEnumerable`1 parameters, Boolean isOptional, Boolean isUnique)
   at Ninject.Extensions.Wcf.NinjectInstanceProvider.GetInstance(InstanceContext instanceContext, Message message) in C:\Development\ninject.extensions.wcf\source\Ninject.Extensions.Wcf\NinjectInstanceProvider.cs:line 75
   at System.ServiceModel.Dispatcher.InstanceBehavior.GetInstance(InstanceContext instanceContext, Message request)
   at System.ServiceModel.InstanceContext.GetServiceInstance(Message message)
   at System.ServiceModel.Dispatcher.InstanceBehavior.EnsureServiceInstance(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage41(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage31(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage3(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage2(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage11(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage1(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)

And here is the code I am using (pared down to only what's relevant):

In TheService.svc (no code-behind):

<%@ ServiceHost Language="C#"
                Debug="true"
                Service="MyServices.TheService"
                Factory="Ninject.Extensions.Wcf.NinjectServiceHostFactory"
                %>

In Global.asax.cs:

public class Global : NinjectWcfApplication
{
    protected override IKernel CreateKernel()
    {
        var kernel = new StandardKernel(new ServiceModule());
        return kernel;
    }
}

In ServiceModule.cs:

internal class ServiceModule : NinjectModule
{
    public override void Load()
    {
        Bind<ITheService>().To<TheService>();
        Bind<ITheRepository>().To<TheRepository>();
    }
}

All of this code appears to work fine. I put some diagnostics in to trace the method calls and the CreateKernel method is called, followed by the call to the Load method in ServiceModule which returns then CreateKernel returns. However, I get the above exception when I try to call any of the service methods in TheService.

I'm using wsHttpBinding and the service references all resolve just fine. The interfaces and implementation classes are valid. It appears the problem is occurring when the actual service instance is being retrieved from the container/kernel.

What am I missing?

Answer 1

I had the same problem and found that the Kernel was not set in KernelContainer.Kernel (for version 2.2 https://github.com/ninject/ninject.extensions.wcf/blob/2.2.0.0/src/Ninject.Extensions.Wcf/KernelContainer.cs) or (for version 2.3 https://github.com/ninject/ninject.extensions.wcf/blob/2.3.0.0/src/Ninject.Extensions.Wcf/NinjectServiceHostFactory.cs) in NinjectServiceHostFactory.SetKernel(IKernel kernel). Not sure why this isn't magically set, but setting it in the CreateKernel() method in Global.asax seems to fix it.