SharePoint: Set delete behavior on a Lookup Field

SPFieldLookup class includes a RelationshipDeleteBehavior property that enables you to specify the delete behavior for the column.

  • SPRelationshipDeleteBehavior.Cascade
  • SPRelationshipDeleteBehavior.Restrict

private void RestrictDeleteOnLookupField(SPWeb web, string listUrl, Guid fieldGuid)
SPList list = web.GetList(GetListUrl(web.ServerRelativeUrl, listUrl));
SPField field = list.Fields[fieldGuid];
SPFieldLookup fieldLookup = (SPFieldLookup)field;
fieldLookup.Indexed = true;
fieldLookup.RelationshipDeleteBehavior =

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