Dependency Injection in DicomServers

[Jack McKay]

Hello, I am currently planning on using fo-dicom to implement a modern PACS. For keeping the design clean and modular I would prefer to use dependency injection.

When looking at any SCP examples, I see the static Create<T> method is used to create my DicomService, but this method does not (from what I can understand) provide a simple way to support additional constructor parameters.

For example:

Within the PACS I want to implement the DICOM Store Service.

The DICOM Store Service may depend on a database access service, a settings reader, an audit logging service, etc. 

I would rather implement these dependencies as follows:

DicomStoreService : DicomService, IDicomServiceProvider, IDicomCEchoProvider
{
...
    public DicomStoreService(INetworkStream stream, Encoding enc, Logger log, IMyInjectedService a, IMyOtherInjectedService b)
...
    public void OnReceiveAssociationRequest(DicomAssociation association)
    {
        _a.DoSomething(); //Stored instance of IMyInjectedService
        ....
     }
}

Is there a recommended way to achieve this in fo-dicom?

I originally thought of using property injection (after creation of the server) but I would rather stick to constructor injection if possible to prevent instantiation of my services without their dependencies.

Hopefully I've made this clear enough, thanks in advance!

[Anders Gustafsson Cureos AB]

Hello Jack!

Currently there is no support for what you are asking. You are limited to use the 3 parameter constructor for your DicomService implementation. One option you might be able to make use of is that the DicomService base class implements a settable property "object UserState". This could at least be a poor man's solution for what you are trying to achieve?

However, I think your idea is very good, so please feel free to post an issue in the Github repository and we will definitely consider it for implementation.

Regards,

Anders @ Cureos

[Michael W.]

Hi Jack,

I have the same issue regarding DI in SCP service. Did you already add a request in Github project? Did not find anything. Want to ask before I add another request.

Best,
Michael

[Michael W.]

Added issue in github project: https://github.com/fo-dicom/fo-dicom/issues/649