Question

I have a problem with a small app i am writing. Now either my error is in my controller class or its in Routes. See images below.

Controller Class.

This is the default Route i have.

And this is the error i get when i run.
Image not very clear but it says:

The parameters dictionary contains a null entry for parameter ‘playerId’ of non-nullable type ‘System.Int32’ for method ‘System.Web.Mvc.ActionResult Detail(Int32)’ in ‘GlobalUnited.WebUI.Controllers.PlayerController’. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter.
Parameter name: parameters

I read through some posts on here, one particularly:
Similar Link

What exactly does he mean when Daniel Renshaw says:

First, I would suggest you use MVC’s automatic handling of parameters instead ofpulling them out of the Request yourself. Your controller action has an id parameter which seems to go ignored – use that and add others like it to get the input parameters.

Anyways, after reading that post, i changed my RouteConfig file to:

And Still i got this error. It says:

A route named ‘DefaultApi’ is already in the route collection. Route names must be unique.
Parameter name: name

I even tried to change my Detail action parameter to: Note the int? declaration

And i got this error after changing:

Is there something i could do to fix this, something less complicated??
All help will be appreciated, thanks.

Answer 1

Your parameter name playerID causes the problem here. ASP.NET MVC can only provide you a parameter named id using the default route. In your case, it cannot map the request to your action because playerID is not nullable or optional. Changing your parameter name to id will solve the problem.

public ActionResult Detail(int id)

You get the second error with route registration because you already have a route named “DefaultApi”. You won’t need this route if you change the parameter name(also it’s registered elsewhere).

Third error is for trying to querying with the null value. ASP.NET MVC cannot map the value in URL to your parameter and you get the default value null. Since there isn’t a row with a null value you get an empty sequence, then Single() method throws an exception.