With ASP.net Web API 2 install Microsoft ASP.NET Cross Origin support via nuget.
http://enable-cors.org/server_aspnet.html
public static void Register(HttpConfiguration config)
{
var enableCorsAttribute = new EnableCorsAttribute("http://mydomain.com",
"Origin, Content-Type, Accept",
"GET, PUT, POST, DELETE, OPTIONS");
config.EnableCors(enableCorsAttribute);
}