Select execution not working for financial period

Regarding error message Model.cs not found, additional context is needed. As Acumatica has more then one model class.

Overall, without context, which I asked you before,  I can suggest something like this:

    public class YourGraph : PXGraph<YourGraph>
    {
        public PXFilter<FinPeriodFilter> Filter;

        public PXSelect<FinPeriod,
            Where<FinPeriod.startDate, LessEqual<Current<FinPeriodFilter.fromDate>>,
                And<FinPeriod.endDate, GreaterEqual<Current<FinPeriodFilter.fromDate>>>>> FinPeriods;

        public virtual IEnumerable finPeriods()
        {
            FinPeriodFilter filter = Filter.Current;
            if (filter != null && filter.FromDate != null)
            {
                foreach (FinPeriod period in PXSelect<FinPeriod,
                                 Where<FinPeriod.startDate, LessEqual<Required<FinPeriodFilter.fromDate>>,
                                     And<FinPeriod.endDate, GreaterEqual<Required<FinPeriodFilter.fromDate>>>>>
                             .Select(this, filter.FromDate, filter.FromDate))
                {
                    yield return period;
                }
            }
        }
    }

    public class FinPeriodFilter : IBqlTable
    {
        #region FromDate
        public abstract class fromDate : PX.Data.BQL.BqlDateTime.Field<fromDate> { }

        [PXDate]
        [PXUIField(DisplayName = "From Date")]
        public virtual DateTime? FromDate { get; set; }
        #endregion
    }

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