LINQ to Entities不支持指定的类型成员'TimeBandDescription'

我有看起来像此错误得到错误的代码：LINQ to Entities不支持指定的类型成员'TimeBandDescription'。仅支持初始化程序，实体成员和实体导航属性。我如何使这个AsEnuermable？

public partial class TimeBand
{
    public TimeBand()
    {
    }

    public int Id { get; set; }

    public string Name { get; set; }

    public long From { get; set; }

    public long To { get; set; }

    [NotMapped]
    public string TimeBandDescription => $"{Name} ({TicksToHhMmFormat(From)} - {TicksToHhMmFormat(To)})";

    private static string TicksToHhMmFormat(long ticks)
    {
        if (ticks == long.MaxValue)
        {
            return "Max";
        }
        var timeSpan = new TimeSpan(ticks);
        return $"{(int)timeSpan.TotalHours}{timeSpan.ToString(@"\:mm")}";
    }
}

public class SuplierService : ISuplierService
{
        public SupplierInfoModel GetSupplierList(int supplierId)
            {
                var query = (from s in suppliers
                             join tb in TimeBands on s.fkTimeBandId equals tb.Id
                             where s.supplierId == supplierId
                             select new SupplierInfoModel
                             {
                                 SupplierId = supplierId,
                                 SupplierEmail = s.Email,
                                 Phone = s.Phone,
                                 Fax = s.Fax,
                                 TimeBandDescription = tb.TimeBandDescription,