VirtualMaint.cs

  public class YearGroupMaint : PXGraph<YearGroupMaint>
  {
		public PXFilter<YearFilter> Filter;
		//[PXVirtualDAC]
		public PXSelect<VirtualComparasion> Comparasions;
		public PXSelect<YearGroup, Where<YearGroup.year, Equal<Required<YearGroup.year>>, Or<YearGroup.year, Equal<Required<YearGroup.year>>>>> YearGroups;

		public PXCancel<YearFilter> Cancel;

		public IEnumerable comparasions()
		{
			YearFilter filter = Filter.Current;
			if(filter.Year == null) yield break;

			Boolean found = false;
			//Checking cache for existing items
			foreach (VirtualComparasion row in Comparasions.Cache.Cached)
			{
				found = true;
				yield return row;
			}

			if (!found) //if not found - Select from DB
			{
				Comparasions.Cache.Clear();
				foreach (YearGroup row in YearGroups.Select(filter.Year, Accessinfo.BusinessDate.Value.Year))
				{
					VirtualComparasion key = new VirtualComparasion() { Group = row.Group, ComparasionYear = 0, CurrentYear = 0 };
					VirtualComparasion value = (Comparasions.Cache.Locate(key) ?? Comparasions.Cache.Insert(key)) as VirtualComparasion;
					
					if (row.Year == filter.Year) value.ComparasionYear += row.Value.Value;
					if (row.Year == Accessinfo.BusinessDate.Value.Year) value.CurrentYear += row.Value.Value;
					
					value = Comparasions.Update(value);
					Comparasions.Cache.SetStatus(value, PXEntryStatus.Held);
				}
				foreach (VirtualComparasion row in Comparasions.Cache.Cached)
					yield return row;

				Comparasions.Cache.IsDirty = false;
			}
		}

		public virtual void YearFilter_Year_FieldUpdated(PXCache sender, PXFieldUpdatedEventArgs e)
		{
			Comparasions.Cache.Clear();
		}
	}