Unity unable to resolve a dependency of InterfaceInterceptor

Question

I have written an implementation of the unity interface IInterceptionBehavior to do some logging. It has a dependency on an ILog to do the logging.

public class InterceptionLoggingBehavior : IInterceptionBehavior {
  public InterceptionLoggingBehavior(ILog log) {...}
  ...
}

I also have a ConsoleLog that implements ILog.

I am trying to resolve an interface that uses the logging interface interceptor, but it cannot find the ILog. Trying to resolve the InterceptionLoggingBehavior directly does not work even though I can get unity to resolve the ILog directly:

UnityContainer container = ...
var l = container.Resolve<com.InsightSoftware.LoggingAPI.ILog>();
var b = container.Resolve<com.InsightSoftware.Logging.InterceptionLoggingBehavior>();
var p = container.Resolve<com.InsightSoftware.MetadataAPI.ITableIdentityProvider>();

Resolving the ILog (on the second line) works fine, but resolving the InterceptionLoggingBehavior on the 3rd line or the ITableIdentityProvider (the interface that I am trying to log) on the 4th line gets the error:

The current type, com.InsightSoftware.LoggingAPI.ILog, is an interface and cannot be constructed. Are you missing a type mapping?

My Question: Can anyone tell me why unity cannot resolve the ILog when it is a dependency for InterceptionLoggingBehavior?

The xml that I am using to configure unity, including the mapping:

<unity xmlns="http://schemas.microsoft.com/practices/2010/unity">
<sectionExtension type="Microsoft.Practices.Unity.InterceptionExtension.Configuration.InterceptionConfigurationExtension, Microsoft.Practices.Unity.Interception.Configuration" />

<alias alias="ILog"                                 type="com.InsightSoftware.LoggingAPI.ILog, com.InsightSoftware.LoggingAPI"/>
<alias alias="ConcreteLog"                          type="HubbleSandbox.ConsoleLog, HubbleSandbox" />
<alias alias="InterceptionLoggingBehavior"          type="com.InsightSoftware.Logging.InterceptionLoggingBehavior, com.InsightSoftware.Logging" />
<!--More aliases-->
<containers>
  <container>
    <extension type="Interception" />

    <!-- The type mapping that I expect to be resolved. -->
    <register type="ILog"                           mapTo="ConcreteLog" />

    <register type="ITableIdentityProvider"         mapTo="TableIdentityProvider">
      <interceptor type="InterfaceInterceptor"/>
      <interceptionBehavior type="InterceptionLoggingBehavior" />
    </register>
    <!--More registrations-->
  </container>
</containers>

(note that I never explicitly register InterceptionLoggingBehavior, I think that it gets implicitly registered by using it in the interceptionBehavior tag.)

I've also tried configuring unity in code (not using a config file) like so:

UnityContainer container = new UnityContainer();
container.AddNewExtension<Interception>();
container.RegisterType<ILog, ConsoleLog>();
container.RegisterType<ITableIdentityProvider, TableIdentityProvider>(
    new Interceptor<InterfaceInterceptor>(),
    new InterceptionBehavior<InterceptionLoggingBehavior>());
// more registrations

var l = container.Resolve<ILog>();
var b = container.Resolve<ITableIdentityProvider>();

but I still get the same error.

Edit/Update I've done some more digging and tried replacing the line where I resolve the InterceptionLoggingBehavior with

container.Resolve<InterceptionLoggingBehavior>(
  new ParameterOverride(
    "log", 
    container.Resolve<ILog>()));

and I get the error

Resolution of the dependency failed, type = \"com.InsightSoftware.Logging.InterceptionLoggingBehavior\", name = \"(none)\".

Exception occurred while: Resolving parameter \"log\" of constructor com.InsightSoftware.Logging.InterceptionLoggingBehavior(com.InsightSoftware.LoggingAPI.ILog log).

Exception is: InvalidCastException - Unable to cast object of type 'HubbleSandbox.ConsoleLog' to type 'com.InsightSoftware.LoggingAPI.ILog'.

I've checked that the types are assignable.

public class ConsoleLog : ILog {...

and

ILog l = new ConsoleLog();

Neither cause any error. I've also checked that the namespaces are correct (ILog is a common interface name - we are using our ILog as a facade to the ILog in log4Net - so I have triple checked).

Using

.Net Framework 4.5
Unity 2.1.505.0 (we are having problems with the latest Unity on mono)
Some dependencies are from internal NuGets - not sure if this is a factor

Interesting. My first thought was that the interceptor is an element of the infrastructure, rather than one of resolvable services. And I am not sure Unity applies the same resolution logic to both your business classes and infrastructure classes. In other words, if you resolve the type in an explicit way, it works. If Unity uses it internally as an interceptor, are you sure it resolves it using the very same container? — Wiktor Zychla
– Wiktor Zychla, Commented Jul 17, 2014 at 16:25
Good thought, but I get the error when resolving the InterceptionLoggingBehavior from the exact same container as I register the ILog. — Jonny
– Jonny, Commented Jul 18, 2014 at 8:30
Ok, I've created a minimal setup that follows your scenario and it works for me. No exception. I think you are doing something yet more specific. — Wiktor Zychla
– Wiktor Zychla, Commented Jul 18, 2014 at 12:21

Jonny · Accepted Answer · 2014-07-21 16:27:40Z

I've found the answer to my own question after a little more digging, so I shall post it in case anyone else finds that they have the exact same problem.

The setup that I am using involves three separate solutions:

A logging API solution (very simple)
An implementation of that API that uses unity interface interception to do logging (has a dependency on 1)
A sandbox that ties the two of them together and provides a default implementation of ILog (has a dependency on 1 and 2)

1 and 2 are provided via NuGets

The problem was that I had was that I updated the assembly name (in project properties) of the API project (from LoggingAPI to com.InsightSoftware.LoggingAPI). Then I pushed the API NuGet and then got the latest NuGet in the sandbox project - however I did not remember to get the latest NuGet in the implementation project and re-push that.

As a result the implementation was looking for a class from the LoggingAPI assembly, but getting a class from the com.InsightSoftware.LoggingAPI assembly, and so the types did not match and unity could not resolve the correct type.

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