Provision additional lookup fields with CSOM

When you create a lookup field in SharePoint, you’ll have the option to add additional fields of the source list to your target list. When you create this from the UI, you check those fields on creation of the lookup field. But when you create this from your provision code, you can’t find any parameters on the lookup field itself.

The key for doing this in the code is the method AddDependentLookup on the Fields collection of the target list. To provision this lookup, I created the following method in my provisioner:

private void AddDependantLookup(List parentList, List targetList, Guid lookupFieldId, Field primaryLookupField, string displayName) { Field toField = parentList.Fields.GetById(lookupFieldId); _clientContext.Load(toField); _clientContext.Load(targetList); _clientContext.ExecuteQuery(); Field dependantField = targetList.Fields.AddDependentLookup(displayName, primaryLookupField, toField.StaticName); FieldLookup dependantFieldLookup = _clientContext.CastTo(dependantField); dependantFieldLookup.LookupField = toField.StaticName; dependantField.UpdateAndPushChanges(true); _clientContext.Load(dependantField); _clientContext.ExecuteQuery(); }

Please note that the lookupFieldId should be the fieldId of the field you want to add to your target list, and there should be another ‘primary’ lookup field configured between the two lists. The displayName is free to choose, this one will show up as column heading for instance in your target list.