public static IQueryable <T> UpdateGridModelList <T>(this IQueryable <T> entitySet, GridModel gm)
        {
            if (gm == null)
            {
                return(entitySet);
            }
            gm.Count = entitySet.Count();

            gm.BuildPager();

            var sortDirection = gm.SortDirection;

            if (gm.SortDirection == "DESC")
            {
                gm.SortDirection = "ASC";
            }
            else if (gm.SortDirection == "ASC")
            {
                gm.SortDirection = "DESC";
            }

            return(entitySet.OrderBy(gm.SortKey + " " + sortDirection).Skip((gm.Pager.CurrentPage - 1) * gm.Pager.PageSize).Take(gm.Pager.PageSize));
        }