What is the *exact* error message?
Firstly, if you want the default value of a parameter, pass Missing.Value
rather null or empty string.
Secondly, every time you use multiple dot notation (e.g.
rdoFolder2.FolderFields.Add), you get back a brand new COM object back every
time, so when you call rdoFolder2.FolderFields.Save, you won't get any new
fields. Cache the value of the FolderFields object:

RDOFolder2 rdoFolder2 = (RDOFolder2)rdoFolder;
RDOFolderFields fields = rdoFolder2.FolderFields;
RDOFolderField field =fields.Add("UDF2", rdoUserPropertyType.olText,
Missing.Value, Missing.Value);
fields.Save;

Also try the following VB script (you can run it from "Script Editor" in
OutlookSpy):

set Session = CreateObject("Redemption.RDOSession")
Session.MAPIOBJECT = Application.Session.MAPIOBJECT
set Folder =
Session.GetFolderFromID(Application.ActiveExplorer .CurrentFolder.EntryID)
set FolderFields = Folder.FolderFields
set Field = FolderFields.Add("Redemption Text Prop")
'set Field = FolderFields.Add("Redemption Percent Prop", &HD, ,2)
'olPercent, 2 decimals
set Field = FolderFields.Add("Redemption Number Prop", &HC, ,3) 'olNumber, 2
decimals
FolderFields.Save

Dmitry Streblechenko (MVP)
http://www.dimastr.com/
OutlookSpy - Outlook, CDO
and MAPI Developer Tool

"MA" wrote in message
...
Thanks.

I have tried the following code without any success. The
RDOFolderField - "field" object return null. I have tried without GUID
by passing null value. String.empty on Guid return exception. Any
suggestions?

------------------------------------
RDOFolder2 rdoFolder2 = (RDOFolder2)rdoFolder;
RDOFolderField field = rdoFolder2.FolderFields.Add("UDF2",
Redemption.rdoUserPropertyType.olText, "{00020329-0000-0000-
C000-000000000046}", 0);

if (field != null)
rdoFolder2.FolderFields.Save();
---------------------------------

Regards,
MA