Cascading Lookups in SharePoint

One of the things that makes Microsoft SharePoint potentially useful for Document management is its support for capturing additional metadata for documents, email messages and other files as you save them, together with its support for searching based on metadata. When it comes to capturing metadata, a requirement that occurs quite often is to have 'Cascading' Lookup columns - i.e. the valid values that are displayed for one Lookup column in a document library being dependent on the value you choose for another Lookup column in that same library.

A classic example would be values for a Lookup column called 'Project' being dependent on the choice that you make in a 'Client' Lookup column. In general this Cascading lookup is a way of implementing a hierarchical taxonomy in your SharePoint metadata.

Another name that you sometimes see for a Cascading Lookup is 'Dual Lookup' - which reflects the way values from two Lookup columns need to be linked together.

MacroView has developed a world-class Cascading Lookup for SharePoint, which we have licensed to a number of organizations. This Cascading Lookup ships as a custom field type, which will work both in the SharePoint web browser UI and also in MacroView's WISDOM DMF add-on for enhanced document management in SharePoint. The screen shot on the left shows WISDOM's Profiling dialog being used to capture entries for a COUNTRY column, which is cascading from a REGION column.

The MacroView Cascading Lookup has a number of nice features:

1) The valid values for both Lookups are retrieved from standard Lists in SharePoint, which makes maintenance really easy to manage (See sample List on the right);

2) Valid values in the 'top' lookup can be filtered so that only those with an Active flag set to 'Yes' are displayed (this allows you to block access to values that are no longer relevant without causing errors in already saved files);

3) Valid values can be further filtered by an optional CAML query;

4) The 'bottom' or dependent lookup can be multi-select;

5) Cascading Lookup can be configured at Site Collection level;

6) Cascading Lookup columns can be included in library templates;

7) The user's recent selections are displayed at the top of the list of valid values (This Recent Selections feature is common to all Lookup columns in WISDOM DMF, and can really reduce the effort associated with re-selecting a value in a Lookup column that has a large number of valid values).