SharePoint CSOM: How to update person or group field using ValidateUpdateListItem?
I am updating a SharePoint list item using the ValidateUpdateListItem method of the client-side object model to prevent creation of a new item version. This basically works fine for all fields except the ones with person or group field type. Does anyone know what is the correct string representation of a user or group value to be used as FieldValue of an ListItemFormUpdateValue object? I have already tried everything that seems reasonable to me (user ID from User Info, login name, lookup-value like combinations of these data etc.) without any success.
Answer
I just ran into a problem where updating more than 12 person or group fields with item update caused it to throw an exception. Apparently this is caused due to the list view look up threshold in SP online (12 as of this date).
http://blog.vanmeeuwen-online.nl/2012/07/value-does-not-fall-within-expected.html
To work around that I used the ValidateUpdateListItem method to update the person or group ids. The trick is to assign it a json in the format of
[{"Key":"i:0#.f|membership|[email protected]"}]
formValues.Add(new ListItemFormUpdateValue() { FieldName = "AssignedTo", FieldValue = "[{'Key':'i:0#.f|membership|[email protected]'}]" });
For multiple values, it can be comma separated. Have not tried it with group but i think it should work.
Hopefully this can be useful for someone.