During server processing the BeforeExtract and AfterExtract for each folder field and for each folder are fired. These events can be used analogously to the document processing for setting field values like in the following example: Summarizing the a specific document field of all documents in a folder and writing this sum to a folder field.

Private Sub SupplierTotal_BeforeExtract(pXFolder As CASCADELib.CscXFolder, pField As CASCADELib.CscXFolderField, pSkip As Boolean)

   Dim i As Long
   Dim dSupplierTotal As Double

   For i = pXFolder.DocInfos.Count - 1 To 0 Step -1
      dSupplierTotal = dSupplierTotal + pXFolder.DocInfos(i).XDocument.Fields.ItemByName("Total").DoubleValue
   Next i

   pField.Text = CStr(dSupplierTotal)
   pField.ExtractionConfident = True

End Sub

During validation a different event is needed to keep this folder field up to date. Use the event AfterFieldConfirmed of the ValidationForm object to update the folder field data from the document data.

Private Sub ValidationForm_AfterFieldConfirmed(pXDoc As CASCADELib.CscXDocument, pField As CASCADELib.CscXDocField)

   If pField.Name = "Total" Then
      pXDoc.ParentFolder.Fields.ItemByName("SupplierTotal").Text = Format(RecalculateTotal(pXDoc),"#.###,00")
   End If

End Sub

Private Function RecalculateTotal(pXDoc As CASCADELib.CscXDocument) As Double

   Dim oXDocInfo As CASCADELib.CscXDocInfo
   Dim n As Integer

   RecalculateTotal = 0

   For n = 0 To pXDoc.ParentFolder.DocInfos.Count - 1
      Set oXDocInfo = pXDoc.ParentFolder.DocInfos(n)
      RecalculateTotal = RecalculateTotal + oXDocInfo.XDocument.Fields.ItemByName("Total")
   Next n

End Function