Why am I getting 404 when the route matches? ASP.Net MVC - asp.net

Question

I have been stuck on this issue for several hours now.
I have a controller called 'DecisionPoint' and I have a breakpoint set on it's 'ApplicationState' action. No matter what I try I keep getting a 404 in the browser. I suspected that my route was not correct so I downloaded a route debugger and it turns our the URLs I am trying match the Controller and the action. So why do I get a 404 and never see the breakpoint hit?
/DecisionPoint/ApplicationState/no/worky --> 404
Controller:
public ActionResult ApplicationState(string fileName, string stateString)
{
string filePath = GetDpFilePath(fileName);
HtmlDocument htmlDocument = new HtmlDocument();
htmlDocument.Load(filePath);
HtmlNode stateScriptNode =
htmlDocument.DocumentNode.SelectSingleNode("/html/head/script[#id ='applicationState']");
stateScriptNode.InnerHtml = "var applicationStateJSON =" + stateString;
htmlDocument.Save(filePath);
return Json("State Updated");
Route
routes.MapRoute(
"DecisionPointState", // Route name
"DecisionPoint/ApplicationState/{fileName}/{stateString}", // URL with parameters
new {controller = "DecisionPoint", action = "ApplicationState"} // Parameter defaults
);
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
);
}`
**Update**
I create a whole new controller and it works. This is now what my route table looks like. The state controller correclty routes to SaveState
public static void RegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.MapRoute(
"StateRoute", // Route name
"State/SaveState/{file}/{state}", // URL with parameters
new { controller = "State", action = "SaveState", file = UrlParameter.Optional, state = UrlParameter.Optional } // Parameter defaults
);
routes.MapRoute(
"DPStateRoute", // Route name
"DecisionPoint/ApplicationState/{file}/{state}", // URL with parameters
new { controller = "DecisionPoint", action = "ApplicationState", file = UrlParameter.Optional, state = UrlParameter.Optional } // Parameter defaults
);
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
);
}
protected void Application_Start()
{
AreaRegistration.RegisterAllAreas();
RegisterRoutes(RouteTable.Routes);
// RouteDebug.RouteDebugger.RewriteRoutesForTesting(RouteTable.Routes);
}
}
So I am stumped..

Answer 1

Make sure your controller class is called DecisionPointController and not DecisionPoint

Answer 2

If your AreaRegistration class and Controller class are not in the same namespace, you'll be in this situation - the route will match (and RouteDebugger will confirm this) but you'll get a 404 at the "correct" url.
The solution is to make sure both clases are in the same namespace.

Answer 3

This can happen due to your Controller being in another project which references a different version of System.Web.Mvc!
I had the same symptoms - the correct route was found, but got a 404! On HttpHandler.ProcessRequest, an exception was thrown saying the handler's controller does not implement IController.

Answer 4

I just recently ran into this same problem. For me the problem was that I had two controllers with the same name if different namespaces (One was in an area).

Answer 5

Dumb, but it got me:
Be sure your controller inherits from Controller

Answer 6

I'm no routes guru, but I have always added all parameters for the default argument:
routes.MapRoute(
"DecisionPointState", // Route name
"DecisionPoint/ApplicationState/{fileName}/{stateString}", // URL with parameters
new {controller = "DecisionPoint",
action = "ApplicationState"
fileName = UrlParameter.Optional,
stateString = UrlParameter.Optional
} // Parameter defaults
);

Answer 7

In my case, the answer for the same problem was a matter of needing to "include in project" the relevant controllers and views instead of incorrect routing rules.
When mine were created, they weren't automatically included for some reason. This problem was revealed after I closed and re-opened the solution.
{+1 hate} awarded to Visual Studio for its faulty hyper-automation sending me digging through Web.Config files, trying to tack on extensions, and even trying (and failing) to whip up a decent ErrorController.

Answer 8

I was missing
app.MapControllers();
in my program.cs (.NET 6 and above)