I have the following field definition in the Schema.XML file for a custom list definition. Per the documentation setting EnforceUniqueValues and Indexed to true should enforce a uniqueness constraint on the field, but I am able to add duplicate values across list items through the UI.

      <Field Type="Text" 
             RowOrdinal="0" />    

Am I doing something wrong here? Is there somewhere else I need to set this attribute?

  • Curious. Was this in the context of a Sandboxed or Farm solution? – Brian Apr 3 '12 at 16:25
  • It was a farm solution. – JohnFx Apr 3 '12 at 18:33

Have you tried this for other fields than Title?

The spec for SPField.EnforceUniqueValues states that

You cannot set this property to true for a built-in field or for a site column.

Not 100% that this is valid for the declarative approachs for custom schemas, but test with another field "test" of type text and you will find out...

EDIT: - Built-in field can be set EnforceUniqueValues=TRUE. We have to also set Indexed=TRUE & AllowDuplicateValues=False. See Remarks here and answer here.

| improve this answer | |
  • 1
    Ugh. I bet that's it. SharePoint is a minefield of stuff like this. – JohnFx Jun 22 '11 at 22:41
  • built-in field can be set EnforceUniqueValues=TRUE ... We have to also set Indexed=TRUE & AllowDuplicateValues=False .. Read Remarks Here >> msdn.microsoft.com/en-us/library/… – Ronak Patel Dec 13 '16 at 11:02

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