Use ValueTask for DynamicRouteValuesTransformer

src/Mvc/Mvc.Core/ref/Microsoft.AspNetCore.Mvc.Core.netcoreapp3.0.cs

@@ -2914,7 +2914,7 @@ namespace Microsoft.AspNetCore.Mvc.Routing
     public abstract partial class DynamicRouteValueTransformer
     {
         protected DynamicRouteValueTransformer() { }
-        public abstract System.Threading.Tasks.Task<Microsoft.AspNetCore.Routing.RouteValueDictionary> TransformAsync(Microsoft.AspNetCore.Http.HttpContext httpContext, Microsoft.AspNetCore.Routing.RouteValueDictionary values);
+        public abstract System.Threading.Tasks.ValueTask<Microsoft.AspNetCore.Routing.RouteValueDictionary> TransformAsync(Microsoft.AspNetCore.Http.HttpContext httpContext, Microsoft.AspNetCore.Routing.RouteValueDictionary values);
     }
     [System.AttributeUsageAttribute(System.AttributeTargets.Method, AllowMultiple=true, Inherited=true)]
     public abstract partial class HttpMethodAttribute : System.Attribute, Microsoft.AspNetCore.Mvc.Routing.IActionHttpMethodProvider, Microsoft.AspNetCore.Mvc.Routing.IRouteTemplateProvider

src/Mvc/Mvc.Core/src/Routing/DynamicRouteValueTransformer.cs

@@ -37,6 +37,6 @@ namespace Microsoft.AspNetCore.Mvc.Routing
         /// <param name="httpContext">The <see cref="HttpContext" /> associated with the current request.</param>
         /// <param name="values">The route values associated with the current match. Implementations should not modify <paramref name="values"/>.</param>
         /// <returns>A task which asynchronously returns a set of route values.</returns>
-        public abstract Task<RouteValueDictionary> TransformAsync(HttpContext httpContext, RouteValueDictionary values);
+        public abstract ValueTask<RouteValueDictionary> TransformAsync(HttpContext httpContext, RouteValueDictionary values);
     }
 }

src/Mvc/test/WebSites/RoutingWebSite/StartupForDynamic.cs

@@ -48,7 +48,7 @@ namespace RoutingWebSite
         private class Transformer : DynamicRouteValueTransformer
         {
             // Turns a format like `controller=Home,action=Index` into an RVD
-            public override Task<RouteValueDictionary> TransformAsync(HttpContext httpContext, RouteValueDictionary values)
+            public override ValueTask<RouteValueDictionary> TransformAsync(HttpContext httpContext, RouteValueDictionary values)
             {
                 var kvps = ((string)values["slug"]).Split(",");
 
@@ -59,7 +59,7 @@ namespace RoutingWebSite
                     results[split[0]] = split[1];
                 }
 
-                return Task.FromResult(results);
+                return new ValueTask<RouteValueDictionary>(results);
             }
         }
     }