Question

I have a reporting MVC application that uses Castle Windsor.

On application start up (in global.asax) all of the types are registered and then each subsequent request to the application resolves the relevant report type and windsor automatically handles the dependencies.

I need to switch one of the dependant types for another depending on a parameter passed in on the request.

How can I achieve this?

I have registered a factory method with windsor to handle the resolution of the switchable types but as this is registered on application start how can I pass a parameter to the factory method when the parameter is only available on a later request?

If I try registering the factory for each request it works on the first request but then complains on all subsequent requests that the factory is already registered. Unregistering the factory after each request doesnt sound like the right thing to be doing.

Answer 1

When you need to resolve types at runtime, the normal solution is to inject a factory that can make the decision at the appropriate time:

public class ReportFactory: IReportFactory {
    IReport CreateReport(bool useDefault) {
        if (useDefault) {
            return new DefaultReport();
        } else {
            return new UnusualReport();
        }
    }
}

Classes that previously required an IReport should demand an IReportFactory instead.