Custom Control: MultiValue Field
Multiple values fields have become a necessity in work items. I noticed a lot of people searching for this readymade field all over the Team System community, in order to enable saving more than 1 value chosen from a drop down list.
Here is my suggestion for this kind of a field to be combined in your work item XML template: Linked here is a ZIP file which contains the solution for this custom control.
In addition to the code, I included in this ZIP a short READ ME file for explanations with brief instructions of implementation (It is extremely important that you read this file before you start implementing this custom control).
Enjoy!
(For general information about creating custom controls see Narens' blog).