Controlar Authorization en WebApi C#

Agregar con NuGet el package: Microsoft.AspNet.WebApi.Cors

En un WebApi:

using System.Web.Http.Cors;

var cors = new EnableCorsAttribute("*", "*", "*");
config.EnableCors(cors);

config.Formatters.JsonFormatter.SupportedMediaTypes
.Add(new MediaTypeHeaderValue("text/html"));

config.Filters.Add(new FiltroAuth());