Inject different repository depending on a querystring / derive controller and inject the repository depending on the controller type / ASP.NET MVC

Question

I have a search form that can search in different provider. I started out by having a base controller

public SearchController : Controller
{

    protected r         


        

Answer 1

Whenever you need to vary a dependency based on a run-time value, Abstract Factory is the general solution.

Instead of injecting ISearchService into your Controllers, inject an ISearchServiceFactory:

public SearchController : Controller 
{ 
    private readonly ISearchServiceFactory searchServiceFactory;

    public SearchController(ISearchServiceFactory searchServiceFactory) 
    { 
        if (searchServiceFactory == null)
        {
            throw new ArgumentNullException("searchServiceFactory");
        }

        this.searchServiceFactory = searchServiceFactory; 
    } 

    public ActionResult Search(...) 
    { 
        // Use searchServiceFactory to create an ISearchService based on
        // run-time values, and use it to query and return a view. 
    } 
} 

It is not entirely clear to me which run-time value you need to vary on, but assuming that it's the Query, ISearchServiceFactory might be defined like this:

public interface ISearchServiceFactory
{
    ISearchService Create(Query query);
}