MVC Attribute allowing cross-domain requests

AllowCrossDomainJsonAttribute.cs

using System.Linq;
using System.Web.Mvc;

namespace Common.Helpers
{
    public class AllowCrossDomainJsonAttribute : ActionFilterAttribute
    {
        const string Origin = "Origin";
        const string AccessControlAllowOrigin = "Access-Control-Allow-Origin";
        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            var request = filterContext.RequestContext.HttpContext.Request;
            if (request.Headers != null)
            {
                filterContext.RequestContext.HttpContext.Response.AddHeader(AccessControlAllowOrigin, request.Headers.GetValues(Origin).First());
            }
            base.OnActionExecuting(filterContext);
        }
    }
}