ASP.NET WebAPI: Generic controller for OData endpoint

Question

I'm currently experimenting with OData endpoints in ASP.NET MVC 4 Web API. I like the concept and try to come up with efficient ways to use it in our project. One question I have is the following: we have a service that is able to return an IQueryable and takes the name of an entity as Input:

public IQueryable GetAll(string entityName);

In standard Web API (as opposed to OData Controllers) I can create a generic controller, that can be called in the form /api/entities/{entityName} and returns the IQueryable. In case of an OData Controller, I carry out the following entity-specific steps:

1. Register the entities in the model.
2. Create a separate Controller for each entity that derives from EntitySetController<>.

I want to use the generic service and avoid as much entity-specific implementations as possible. The first step can easily be automated if the service can return a list of the entities and the corresponding types. That leaves step 2, because up to now I need to create a specific controller for each entity. I also want to avoid that and create a generic controller that uses the generic service.

Can anyone recommend a solution, maybe by influencing OData routing?

Answer 1

You can create a custom routing convention that selects the same controller no matter what the entity set is. Example,

public class CustomControllerRoutingConvention : IODataRoutingConvention
{
    public string SelectAction(ODataPath odataPath, HttpControllerContext controllerContext, ILookup<string, HttpActionDescriptor> actionMap)
    {
        return null;
    }

    public string SelectController(ODataPath odataPath, HttpRequestMessage request)
    {
        return "SomeFixedContrllerNameWithoutTheControllerSuffix";
    }
}

You can register that routing convention using the following code,

IList<IODataRoutingConvention> routingConventions = ODataRoutingConventions.CreateDefault();
routingConventions.Insert(0, new CustomControllerRoutingConvention());
config.Routes.MapODataRoute("OData", "odata", builder.GetEdmModel(), new DefaultODataPathHandler(), routingConventions);