Thanks to all who came to my REST talk at Oredev

The slides are here

REST.pdf (325.61 KB)

and the demos are here

REST.zip (30.32 KB)

I'm going to be doing a couple of sessions at the Oredev conference in Sweden in November

Writing REST based Systems with .NET

For many, building large scale service based systems equate to using SOAP. There is, however, another way to architect service based systems by embracing the model the web uses - REpresentational State Transfer, or REST. .NET 3.5 introduced a way of building the service side with WCF - however you can also use ASP.NET's infrastructure as well. In this session we talk about what REST is, two approaches to creating REST based services and how you can consume these services very simply with LINQ to XML.

I've been looking at the routing infrastructure Microsoft are releasing in .NET 3.5 SP1. This is the infrastructure that allows me to bind an HTTP Hander to a URI rather than simply using webforms. It is used in the ASP.NET MVC framework that is in development. The infrastructure is pretty clean in design, First you add a reference to System.Web.Routing. Then you simply create Route objects binding a URI to an implementation of IRouteHandler. Finally you add it to a RouteTable static class. Global.asax is the ideal spot for this code.

void Application_Start(object sender, EventArgs e) 
{
        Route r = new Route("books", new BooksRouteHandler());
        RouteTable.Routes.Add(r);
        r = new Route("books/isbn/{isbn}", new BooksRouteHandler());
        RouteTable.Routes.Add(r);
        r = new Route("search/price", new SearchRouteHandler());
        RouteTable.Routes.Add(r);
}

Here BooksRouteHandler and SearchRouteHandler implement IRouteHandler

public interface IRouteHandler
{
    IHttpHandler GetHttpHandler(RequestContext requestContext);
}

So for example the BooksRouteHandler looks like this

public class BooksRouteHandler : IRouteHandler
{
    public IHttpHandler GetHttpHandler(RequestContext requestContext)
    {
        if (requestContext.RouteData.Values.ContainsKey("isbn"))
        {
            string isbn = (string)requestContext.RouteData.Values["isbn"];
            returnnew ISBNHandler(isbn);
        }
        else
        {
            return new BooksHandler();
        }
    }
}

Where ISBNHandler and BooksHandler both implement IHttpHandler

This is all pretty straightforward. The one thing that had me puzzling for a while is who looks at the RouteTable. Reflector to the rescue! There is a module in the System.Web.Routing assembly called UrlRoutingModule. If you add this in to your web.config the routing starts working. The config piece looks like this

<httpModules>
      <add name="Routing" 
           type="System.Web.Routing.UrlRoutingModule, System.Web.Routing, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
</httpModules>