/// <summary>
 /// Adiciona uma mensagem de valor requerido para o estado da model.
 /// </summary>
 /// <param name="controllerContext"></param>
 /// <param name="modelState"></param>
 /// <param name="modelStateKey"></param>
 /// <param name="elementType"></param>
 /// <param name="value"></param>
 private static void AddValueRequiredMessageToModelState(System.Web.Mvc.ControllerContext controllerContext, System.Web.Mvc.ModelStateDictionary modelState, string modelStateKey, Type elementType, object value)
 {
     if (((value == null) && !TypeHelpers.TypeAllowsNullValue(elementType)) && modelState.IsValidField(modelStateKey))
     {
         modelState.AddModelError(modelStateKey, GetValueRequiredResource(controllerContext));
     }
 }