Drum - Direct Route URI Maker for ASP.NET Web API

Drum is a little library for building URIs to ASP.NET Web API actions, using direct routes and lambda expressions. It provides an alternative to the UrlHelper class. Instead of requiring a route name and a set of name-value pairs, Drum allows the creation of URIs using actions invocations.

// using UrlHelper 
var uri1 = _urlHelper.Link("GetPaged", new { page = 0, count = 10 });

// using UriMaker
var uri2 = _uriMaker.UriFor(c => c.GetPaged(0, 10));

where GetPaged is a Web API controller action

[RoutePrefix("api/UriMakerTests/resources")]
public class ResourceController : ApiController
{
    [Route("", Name="GetPaged")]
    public HttpResponseMessage GetPaged(int page, int count) {...}

    ...
}

The idea of using lambda expressions to generated URIs is not a new one.

• In the following post, José Romanielo creates a typed resource linker for a WCF Web API preview: http://joseoncode.com/2011/03/18/wcf-web-api-strongly-typed-resource-linker

• The Hyprlinkr library provides a RouteLinker class for creating URIs based on lambda expressions. By default, it assumes that there is only a single configured route named "API Default". Different behaviors require the injection of a new route dispatcher implementation.

On the other hand, Drum was created to work with direct routes, which were introduced on Web API 2, with the name of attribute routes. This type of routing was generalized on Web API 2.2, allowing for alternative route definition mechanisms. For an example called Strathweb.TypedRouting, see the following post by Filip W.:http://www.strathweb.com/2014/07/building-strongly-typed-route-provider-asp-net-web-api/.

Drum aims to work with any routing mechanism based on direct routes. Drum also works with unnamed routes.

By default, attribute-based direct routes are enabled by calling the MapHttpAttributeRoutes extension method over the HttpConfiguration. To use Drum, use the MapHttpAttributeRoutesAndUseUriMaker method intead.

config.MapHttpAttributeRoutesAndUseUriMaker();

If using a custom direct route mechanism, such as Strathweb.TypedRouting, just pass the custom IDirectRouteProvider as a parameter to the MapHttpAttributeRoutesAndUseUriMaker method (see https://github.com/pmhsfelix/drum/blob/master/src/Drum.Tests/StrathWebTypedRouteTests.cs for an example).

config.MapHttpAttributeRoutesAndUseUriMaker(new TypedDirectRouteProvider());

The Drum library provides an UriMaker<TController> class, containing the UriFor method. This method receives an Expression<Action<TController>> and returns an URI pointing to the action invoked on the given lambda expression.

UriMaker instances can be obtained by one of two methods

• Based on the current HTTP request.
• Using dependency injection.

When you register Drum by calling the MapHttpAttributeRoutesAndUseUriMaker method, UriMakerContext instance is stored in the Properties of the HttpConfiguration and available for every incoming HTTP request. When needed, use the TryGetUriMakerFor<TController> to obtain a UriMaker<TController> instance, for instance inside a controller.

var uriMaker = Request.TryGetUriMakerFor<TypedRoutesController>();

Alternatively, a dependency injection container can also be used to provide the UriMaker instances. For that, the context returned by MapHttpAttributeRoutesAndUseUriMaker must be configured on the container as a singleton instance.

The following excerpt shows an example using the Autofac container.

// Autofac
var builder = new ContainerBuilder();
builder.RegisterApiControllers(Assembly.GetExecutingAssembly());

// Web API routes
var uriMakerContext = config.MapHttpAttributeRoutesAndUseUriMaker();
builder.RegisterInstance(uriMakerContext).ExternallyOwned();
builder.RegisterHttpRequestMessage(config);
builder.RegisterGeneric(typeof(UriMaker<>)).AsSelf().InstancePerRequest();

Drum is available as a nuget package at: https://www.nuget.org/packages/Drum/