static GroupComparer CreateGroupHeader (BaseComparer sc)
		{
			var gc = new GroupComparer(sc.ColumnCollection,sc.ListIndex,sc.ObjectArray);
			gc.IndexList = new IndexList();
			return gc;
		}
		string ExtractValue(BaseComparer element,PropertyDescriptor[] groupProperties)
		{
			var rowItem = baseList[element.ListIndex];
			var values = FillComparer(groupProperties, rowItem);
//			return element.ObjectArray[0].ToString();
			return values[0].ToString();
		}