Creating a lookup field via elements.xml

SharePoint, SPField

This is another post to help me remember. And as a reference for all of you, who cannot remember how to create a SPFieldLookup via XML.

<Field ID="{8b26ec41-b6c3-4327-0066-0c18c0768626}" Name="InternalName" StaticName="InternalName" DisplayName="Display Name" Type="Lookup" ShowField="Title" Mult="TRUE" List="Lists/LookupList" Overwrite="TRUE" />

When you provision a SPField via features, do not forget to add Overwrite=”TRUE”! Otherwise you’ll get an exception like this:

0x8107058aFehler beim Binden des Inhaltstyps ‘0x010200C7A18EB120BB4A00892E9E1EE9481C9B0067E475B6FDD54048B347370871443CAD’ an die Liste ‘/sites/rhtest/Lists/LookupList’ für ‘http://rhdevsp2013/sites/rhtest’. Ausnahme ‘0x80070057’.

Unfortunately the MSDN is not very specific about the Overwrite property:

Optional Boolean. Specifies whether the field definition for a new field that is activated on a site (SPWeb) overwrites the field definition for an existing field, in cases where the new field has the same field ID as the existing field. True if the new field overwrites the existing field with the same field ID; otherwise false. The default is false.

Note, however, that if the existing field is read-only, or if it is sealed, then it will not be overwritten by the field that is being activated, even if this attribute is set to true

Hopefully I’ll think about this the next time a lookup field needs to be provisioned…