@foreach (var item in Model.OrderBy(i => i.MESS_TYPE).ThenBy(i => i.MESS_DATE))

CS1061: "Models.GetMessagesByHeadId_Result" не содержит определение для "OrderBy". Не удалось найти метод расширения "OrderBy", принимающий первый аргумент типа "Models.GetMessagesByHeadId_Result" (пропущена директива using или ссылка на сборку?)

return View(db.GetMessagesByHeadId(id).ToList().OrderBy(i => i.MESS_TYPE).ThenBy(i => i.MESS_DATE));

@using System.Data;
@using System.Data.Entity;
@using System.Linq;
@using System.Web.Mvc;
@using System.Net;

@model Models.GetMessagesByHeadId_Result
...
@foreach (var item in Model.OrderBy(i => i.MESS_TYPE).ThenBy(i => i.MESS_DATE))

return View(db.GetMessagesByHeadId(id).ToList().OrderBy(i => i.MESS_TYPE).ThenBy(i => i.MESS_DATE));

        public virtual ObjectResult<GetMessagesByHeadId_Result> GetMessagesByHeadId(Nullable<int> headId)
        {
            var headIdParameter = headId.HasValue ?
                new ObjectParameter("HeadId", headId) :
                new ObjectParameter("HeadId", typeof(int));
    
            return ((IObjectContextAdapter)this).ObjectContext.ExecuteFunction<GetMessagesByHeadId_Result>("GetMessagesByHeadId", headIdParameter);
        }

        public ActionResult Discussion(int id)
        {
            return View(db.GetMessagesByHeadId(id).ToList().OrderBy(i => i.MESS_TYPE).ThenBy(i => i.MESS_DATE));
        }

@model Models.GetMessagesByHeadId_Result

.OrderBy(i => i.MESS_TYPE).ThenBy(i => i.MESS_DATE)