Dependency injection with runtime data

Question

Let's assume that we have a service that needs to be initialized, but then it's a singleton. For example, something like this:

public interface IGraphsContainer
{
    void Initialize(IEnumerable<Graph> initialContent);

    void Add(Graph graph);

    bool Contains(Graph graph);

    IEnumerable<Graph> FindAll(Criteria complexCriteria);
}

Assume that the implemention has no dependencies. So it can be easily binded in a DI container and auto-injected into classes that need it.

This works for me, expect for the fact that I must not forget to initialize the container before using it. It needs some additional code to prevent this. That's why I am not enterily satisfied.

Is there a better solution for this that doesn't require the Initialize method?

EDIT: I was not clear about the singletion. The fact is, it's a singleton in its scope, which is NOT the application scope. Therefore this initialize method is invoked in some other AbstractFactory.

In this case, if Graphs are pulled from a folder and a user decides to change the folder, then we need to change the graphs based on that folder and thereby the initial containers content.

Here's the real example where I'm using this Initialize approach. The underlying algorithm is pretty complex and this is just a half of it. So far I need 3 things to be initialized like this.

Answer 1

Is there a better solution for this that doesn't require the Initialize method?

I see two possible designs:

1.. initialContent should move to the constructor of the impl, and should be injected as a dependency. You should not make Initialize part of IGraphsContainer unless clients are expected to call it. Like so:

public interface IGraphsContainer
{
    void Add(Graph graph);
    bool Contains(Graph graph);
    IEnumerable<Graph> FindAll(Criteria complexCriteria);
}

public class DefaultGraphsContainer : IGraphsContainer
{
    public DefaultGraphsContainer(IEnumerable<Graph> initialContent)
    {
        // ...
    }
}

2.. If clients are expected to call Initialize, I would recommend extracting Initialize into its own interface as an abstract factory. You can then inject IGraphsContainerFactory or IGraphsContainer depending on whether the client should call Create (formerly Initialize) or not. Like so:

public interface IGraphsContainerFactory
{
    IGraphsContainer Create(IEnumerable<Graph> initialContent);
}

public interface IGraphsContainer
{
    void Add(Graph graph);
    bool Contains(Graph graph);
    IEnumerable<Graph> FindAll(Criteria complexCriteria);
}