c# - Attribute routing constraints with no parameters -

i create attribute routing in mvc 5 application 1 simple constraint:

public class useragentconstraint : irouteconstraint {     private string _requireduseragent;      public useragentconstraint(string requireduseragent)     {         _requireduseragent = requireduseragent;     }      public bool match(httpcontextbase httpcontext, route route,          string parametername, routevaluedictionary values,         routedirection routedirection)     {         return httpcontext.request.useragent != null &&                httpcontext.request.useragent.contains(_requireduseragent);     } } 

in mvc 4 able register in way:

routes.maproute("chromeroute", "{*catchall}",   new { controller = "home", action = "index" },   new { customconstraint = new useragentconstraint("chrome") }); 

how can achieve same result using only attribute routing? know can register constraint in way:

var constraintsresolver = new defaultinlineconstraintresolver(); constraintsresolver.constraintmap.add("useragent", typeof(useragentconstraint)); 

but how add route pattern? this:

[route("home/index:useragent(chrome)")] public actionresult index() {} 

doesnt work

review aspnetmvc source code,it can helpful , try review

routecontraintattribute , areaattribute , routeattribute

for example routeconstraintattribute:

https://github.com/aspnet/mvc/blob/dev/src/microsoft.aspnet.mvc.core/routeconstraintattribute.cs

i'm trying figure out how that.