Get the Route Template from IOwinContext

Question

I am looking to get the route template from a request. I am using OwinMiddleware and am overriding the Invoke method accepting the IOwinContext.

public override async Task Invoke(IOwinContext context)
{
    ...
}

Given the Request URL: http://api.mycatservice.com/Cats/1234

I want to get "Cats/{CatId}"

I have unsuccessfully tried converting it using the following approachs:

HttpRequestMessage msg = new HttpRequestMessage(new HttpMethod(context.Request.Method), context.Request.Uri);

HttpContextBase httpContext = context.Get<HttpContextBase>(typeof(HttpContextBase).FullName);

For reference:

Here is a post about how to do this using HttpRequestMessage which I have successfully implemented for another project

Answer 1

I had the same problem, this seems to work. A bit by magic, but so far so good:

public class RouteTemplateMiddleware : OwinMiddleware
{
    private const string HttpRouteDataKey = "MS_SubRoutes";
    private readonly HttpRouteCollection _routes;

    public RouteTemplateMiddleware(OwinMiddleware next, HttpRouteCollection routes) : base(next)
    {
        _routes = routes;
    }

    public override async Task Invoke(IOwinContext context)
    {
        var routeData = _routes.GetRouteData(new HttpRequestMessage(new HttpMethod(context.Request.Method), context.Request.Uri));
        var routeValues = routeData?.Values as System.Web.Http.Routing.HttpRouteValueDictionary;

        var route = routeValues?[HttpRouteDataKey] as System.Web.Http.Routing.IHttpRouteData[];
        var routeTemplate = route?[0].Route.RouteTemplate;

        // ... do something the route template

        await Next.Invoke(context);
    }
}

Register the middleware like so:

public void Configuration(IAppBuilder app)
{
    _httpConfiguration = new HttpConfiguration();
    _httpConfiguration.MapHttpAttributeRoutes();
    ...

    app.Use<RouteTemplateMiddleware>(_httpConfiguration.Routes);
    ...
}