Creating custom RequestContext in ASP.NET MVC - asp.net-mvc-3

Question

I'm creating a CMS using ASP.NET MVC, and by design, I've decided that each plugin (add-on) should have a key in the incoming HTTP request. Thus, I have this general route in my host application:
{pluginKey}/{controller}/{action}/{id}
I've created a custom controller factory which implements IControllerFactory and of course, it has a method to create controllers base on the ReqeustContext and controller name. However, I want to create an artificial HttpContext (alongside all other relevant objects like HttpRequest, RequestContext, RouteData, etc.) so that controllers of plugins won't misinterpret these URL segments wrongly. In other words, I want to cut the first part of the incoming URL, and make plugins think that they're processing this URL:
{controller}/{action}/{id}
How can I achieve this?

Answer 1

While you could create a new implementation of all the context classes, it seems like a bit of overkill. Why not use a derived Route Handler that applies the filtering functionality before returning the HttpHandler? Here's an example:
// To avoid conflicts with similarly named controllers, I find it to be good practice
// to create a route constraint with the set of all plugin names. If you don't have
// this function already, you should be able to access it with reflection (one time
// per app lifecycle) or you hard-code them. The point is to have a regex which ensures
// only valid plugins will get selected
string[] pluginNames = GetPluginNames();
string pluginNameRegex = string.Join("|",pluginNames);
Route pluginRoute = new Route (
url: "{pluginKey}/{controller}/{action}/{id}",
defaults: null,
constraints: new RouteValueDictionary(new { pluginKey = pluginNameRegex }),
routeHandler: new PluginRouteHandler()
});
// The custom route handler can modify your route data after receiving the RequestContext
// and then send it to the appropriate location. Here's an example (markdown code/untested)
// Note: You don't have to inherit from MvcRouteHandler (you could just implement IRouteHandler
// but I'm assuming you want Mvc functionality as the fallback)
public class PluginRouteHandler : MvcRouteHandler
{
public PluginRouteHandler(IControllerFactory controllerFactory)
: base(controllerFactory)
{}
protected override IHttpHandler GetHttpHandler(RequestContext requestContext){
if(ValidatePluginRoute(requestContext))
{
// we are going to remove the pluginKey from the RequestContext, It's probably wise
// to go ahead and add it to HttpContext.Items, in case you need the data later
requestContext.HttpContext.Items["pluginKey"] = requestContext.RouteData.Values["pluginKey"];
// now let's get ride of it, so your controller factory will process the
// requestContext as you have described.
requestContext.Values.Remove("pluginKey");
// the route will now be interpreted as described so let the flow go to the MvcRouteHandler's method
}
return base.GetHttpHandler(requestContext);
}
static bool ValidatePluginRoute(RequestContext requestContext){
return requestContext.RouteData.ContainsKey("pluginKey");
}
}