Question

I’m working on moving an API project from raw http handlers where I’m using periods in the paths:

http://server/collection/id.format

I would like to follow the same URL schema in a Web Api (self-hosted) version, and tried this:

var c = new HttpSelfHostConfiguration(b);
c.Routes.MapHttpRoute(
    name: "DefaultApiRoute",
    routeTemplate: "{controller}/{id}.{format}",
    defaults: new { id = RouteParameter.Optional, format = RouteParameter.Optional },
    constraints: null
);

Unfortunately, that doesn’t seem to resolve (consistent 404’s on /foo, /foo/bar and /foo/bar.txt). A similar pattern using a slash before ‘format’ works fine:

var c = new HttpSelfHostConfiguration(b);
c.Routes.MapHttpRoute(
    name: "DefaultApiRoute",
    routeTemplate: "{controller}/{id}/{format}",
    defaults: new { id = RouteParameter.Optional, format = RouteParameter.Optional },
    constraints: null
);

I haven’t yet delved into the code for the Web Api, and before I do thought I’d ask here to see if this is a known, or perhaps even justified limitation in Web Api.

UPDATE: I neglected to mention that “id” and “format” are strings, which turns out to be important for the solution to this question. Adding a constraint to exclude periods from the “id” token solves the 404 problem.

Answer 1

I am unable to reproduce the problem. This should work. Here’s my setup:

1. Create a new .NET 4.0 Console Application
2. Switch to .NET Framework 4.0 profile
3. Install the Microsoft.AspNet.WebApi.SelfHost NuGet

4. Define a Product

   public class Product
   {
       public int Id { get; set; }
       public string Name { get; set; }
   }
   

5. A corresponding API Controller:

   public class ProductsController : ApiController
   {
       public Product Get(int id)
       {
           return new Product
           {
               Id = id,
               Name = "prd " + id
           };
       }
   }
   

6. And a host:

   class Program
   {
       static void Main(string[] args)
       {
           var config = new HttpSelfHostConfiguration("http://localhost:8080");
   
           config.Routes.MapHttpRoute(
               name: "DefaultApiRoute",
               routeTemplate: "{controller}/{id}.{format}",
               defaults: new { id = RouteParameter.Optional, format = RouteParameter.Optional },
               constraints: null
           );
   
           using (var server = new HttpSelfHostServer(config))
           {
               server.OpenAsync().Wait();
               Console.WriteLine("Press Enter to quit.");
               Console.ReadLine();
           }
       }
   }
   

Now when you run this console application you could navigate to http://localhost:8080/products/123.xml. But of course you could navigate to http://localhost:8080/products/123.json and you will still get XML. So the question is: How to enable content negotiation using a route parameter?

You could do the following:

    class Program
    {
        static void Main(string[] args)
        {
            var config = new HttpSelfHostConfiguration("http://localhost:8080");
            config.Formatters.XmlFormatter.AddUriPathExtensionMapping("xml", "text/html");
            config.Formatters.JsonFormatter.AddUriPathExtensionMapping("json", "application/json");

            config.Routes.MapHttpRoute(
                name: "DefaultApiRoute",
                routeTemplate: "{controller}/{id}.{ext}",
                defaults: new { id = RouteParameter.Optional, formatter = RouteParameter.Optional },
                constraints: null
            );

            using (var server = new HttpSelfHostServer(config))
            {
                server.OpenAsync().Wait();
                Console.WriteLine("Press Enter to quit.");
                Console.ReadLine();
            }
        }
    }

and now you can use the following urls:

http://localhost:8080/products/123.xml
http://localhost:8080/products/123.json

Now you might be wondering what’s the relation between the {ext} route parameter that we used in our route definition and the AddUriPathExtensionMapping method because nowhere we did not specify it. Well, guess what: it’s hardcoded in the UriPathExtensionMapping class to ext and you cannot modify it because it is readonly:

public class UriPathExtensionMapping
{
    public static readonly string UriPathExtensionKey;

    static UriPathExtensionMapping()
    {
        UriPathExtensionKey = "ext";
    }

    ...
}

All this to answer your question:

Can periods be used in Asp.Net Web Api Routes?

Yes.