ASP.NET MVC how to disable debug routes/views in production?

You could also use a filter, eg throw this class somewhere:

    public class DebugOnlyAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(
                                           ActionExecutingContext filterContext)
        {
             #if DEBUG
             #else
                 filterContext.Result = new HttpNotFoundResult();
             #endif
        }
    }

Then you'd be able to just drop into the controller and decorate the action methods (or entire controllers) you need not to show up in production with [DebugOnly].

You could also use filterContext.HttpContext.IsDebuggingEnabled instead of the uglier #if DEBUG I'd just be inclined to use the precompiler directive since the decision is definitely not going to take any CPU cycle that way.

If instead you want a global filter to check everything against a few URLs, register it as a global filter in Global.asax:

public static void RegisterGlobalFilters(GlobalFilterCollection filters) {

    filters.Add(new DebugActionFilter());
}

Then you can just check the URL or whatever you want against the list (App-relative path shown here):

public class DebugActionFilter : IActionFilter
{
    private List<string> DebugUrls = new List<string> {"~/Home/",
                                                        "~/Debug/"}; 
    public void OnActionExecuting(ActionExecutingContext filterContext)
    {
        if (!filterContext.HttpContext.IsDebuggingEnabled 
            && DebugUrls.Contains(
                      filterContext
                     .HttpContext
                     .Request
                     .AppRelativeCurrentExecutionFilePath))
        {
            filterContext.Result = new HttpNotFoundResult();
        }
    }

    public void OnActionExecuted(ActionExecutedContext filterContext)
    {
    }
}

@if (HttpContext.Current.IsDebuggingEnabled)
{
}

Class

public class UrlInformation
{
    [XmlElement(ElementName = "ActionName")]
    public string ActionName { get; set; }

    [XmlElement(ElementName = "ControllerName")]
    public string ControllerName { get; set; }

    [XmlElement(ElementName = "AreaName")]
    public string AreaName { get; set; }
}

Class for XML Serializaion

[XmlTypeAttribute(AnonymousType = true)]
public class clsUrlInformation
{
    [XmlElement("Files")]
    public List<UrlInformation> Url { get; set; }

    public clsUrlInformation()
    {
        Url = new List<UrlInformation>();
    }
}

Sample XML(Define your debug action method/controller/area names here)

<?xml version="1.0" ?>
<Url>
    <Files>
    <AreaName></AreaName>
    <ControllerName>Home</ControllerName>
    <ActionName>Index</ActionName>
    </Files>
    <Files>
    <AreaName></AreaName>
    <ControllerName></ControllerName>
    <ActionName></ActionName>
    </Files>                      
</Url>

Action Filter

public class MyActionClass : ActionFilterAttribute
{
    public override void OnActionExecuting(
                                       ActionExecutingContext filterContext)
    {

Let's say you have XML. XML contains information about Area, Action Method Name and Controller Name

var xml =
@"<?xml version=""1.0"" ?>
<Url>
    <Files>
    <AreaName></AreaName>
    <ControllerName>Home</ControllerName>
    <ActionName>Index</ActionName>
    </Files>
    <Files>
    <AreaName></AreaName>
    <ControllerName></ControllerName>
    <ActionName></ActionName>
    </Files>                      
</Url>";

Doing XML Serialization and convert XML to List of Class.

        var serializer = new XmlSerializer(typeof(clsUrlInformation),
                                 new XmlRootAttribute("Url"));
        using (var stringReader = new StringReader(xml))
        using (var reader = XmlReader.Create(stringReader))
        {
            clsUrlInformation result =
                     (clsUrlInformation)serializer.Deserialize(reader);
            RouteData Route = 
                  filterContext.Controller.ControllerContext.RouteData;
            String controller = Convert.ToString(Route.Values["controller"]);
            String action = Convert.ToString(Route.Values["action"]);
            String area = Convert.ToString(Route.DataTokens["area"]);

Comparing the current action with xml so as to show 404

            foreach (var item in result.Url)
            {
                if (HttpContext.Current.IsDebuggingEnabled    &&
                            controller == item.ControllerName &&
                                action == item.ActionName     &&
                                  area == item.AreaName)
                {
                    filterContext.Result = new HttpNotFoundResult();
                    return;
                }
            }
        }

        base.OnActionExecuting(filterContext);
    }
}

@CristiDiaconescu : Mentioning the debug urls in XML file will be more flexible. WHY? Because, later on you can make modification in your XML to increase/decrease/update the url information without making the code change and without deploying the dll. Isn't that ?