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");
    }
}