在WCF服务实例创建期间处理异常

Question

I am using Unity.Wcf to inject dependencies in the service class and it work fine. But if I configure my dependencies incorrectly an exception is thrown by unity that it cannot build up my service instance which is correct. Does anyone knows where I can handle this exception to log it for example? It's much easier to check the log than debug it every time.

Answer 1

Another way to capture the exception is to override the CreateServiceHost methods in the service factory. Call base.CreateServiceHost() inside of a try...catch block and use your logging component of choice to save the exception to the log. Other than logging the error, the behavior will be the same.

public override ServiceHostBase CreateServiceHost(string constructorString, Uri[] baseAddresses)
{
    try {
        return base.CreateServiceHost(constructorString, baseAddresses);
    }
    catch (Exception ex) {
        // log here
        throw;
    }
}

Answer 2

After some investigations I have found out how the instance is created and it seems there is no way to add logging to it easily. The only way it to either change the source code of Unity.Wcf or to inherit few classes and override default behavior. For those who are interested the logic is following: UnityServiceHostFactory creates UnityServiceHost, UnityServiceHost adds behavior class UnityInstanceProvider, this UnityInstanceProvider has a GetInstance method that creates the service and does Unity resolving. So to log something you need to do one of the following:

1. Substitute this class with yours and inherit both UnityServiceHostFactory and UnityServiceHost
2. Get the sources and change something right in this class (UnityInstanceProvider).