.NET Meanderings - Using the ASP.NET Routing infrastructure in .NET 3.5 SP1

Wednesday, June 18, 2008

Using the ASP.NET Routing infrastructure in .NET 3.5 SP1

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"];
            return new 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

I'm currently using it to build a REST based service for the second part of a two part article for the DevelopMentor DevelopMents newsletter so if you're not on the distribution list for that subscribe!