Domain based routing with ASP.NET Web API

Imagine you are building an API which is “multi-tenant”: the domain name defines the tenant or customer name and should be passed as a route value to your API. An example would be http://customer1.mydomain.com/api/v1/users/1. Customer 2 can use the same API, using http://customer2.mydomain.com/api/v1/users/1. How would you solve routing based on a (sub)domain in your ASP.NET Web API projects?

Almost 2 years ago (wow, time flies), I’ve written a blog post on ASP.NET MVC Domain Routing. Unfortunately, that solution does not work out-of-the-box with ASP.NET Web API. The good news is: it almost works out of the box. The only thing required is adding one simple class:

public class HttpDomainRoute
    : DomainRoute
{
    public HttpDomainRoute(string domain, string url, RouteValueDictionary defaults)
        : base(domain, url, defaults, HttpControllerRouteHandler.Instance)
    {
    }

    public HttpDomainRoute(string domain, string url, object defaults)
        : base(domain, url, new RouteValueDictionary(defaults), HttpControllerRouteHandler.Instance)
    {
    }
}

Using this class, you can now define subdomain routes for your ASP.NET Web API as follows:

RouteTable.Routes.Add(new HttpDomainRoute(
    "{controller}.mydomain.com", // without tenant
    "api/v1/{action}/{id}",
     new { id = RouteParameter.Optional }
));

RouteTable.Routes.Add(new HttpDomainRoute(
    "{tenant}.{controller}.mydomain.com", // with tenant
    "api/v1/{action}/{id}",
     new { id = RouteParameter.Optional }
));

And consuming them in your API controller is as easy as:

public class UsersController
    : ApiController
{
    public string Get()
    {
        var routeData = this.Request.GetRouteData().Values;
        if (routeData.ContainsKey("tenant"))
        {
            return "UsersController, called by tenant " + routeData["tenant"];
        }
        return "UsersController";
    }
}

Here’s a download for you if you want to make use of (sub)domain routes. Enjoy!

WebApiSubdomainRouting.zip (496.64 kb)