ASP.NET MVC Remote Validation

public class TimeCard : IValidatableObject
{
...
[Remote("CheckUserName", "Home", ErrorMessage="Username is invalid")]
public string UserName{get; set;}
...
}

public class HomeController : Controller
{
...
public JsonResult CheckUsername(string username)
{
var result = false;
if(username == "tkhuc")
{
result = true;
}
return Json(result, JsonRequestBehavior.AllowGet);
}