This is part two of the post showing how to create a custom lookup field for SharePoint.
Other pages in this post are:
This part will implement the field editor class.
The SharePoint lookup field is far from perfect. Once configured, it’s not possible to change the list it gets it’s data from. This is a good thing while the list actually exists.
Now, if a user deleted the source list, the lookup field becomes next to useless and will need to be deleted and re-created.
Would it not be good to be able to re-configure it when this happens?
Or, how about when the source list or display field is deleted, items that have values are not deleted but instead display (in views and the item display form) the original value when they were created?
So, if you had a lookup field that retrieved its values from a list called Cities and in another list this column was added and had existing items. With the out of the box lookup field, if you delete the list Cities any fields that depends on this will stop showing the linked data. Wouldn’t it be good if the custom field detected this and showed the lookup values that were set when the item was last updated? When the list exists, the field would then show the current live item. So, if you changed the name of a city, the field would reflect this, delete the item and the original value would be shown.
Read on to find out how…