Trying to assign tags with drop down list

I am trying to add tags to my VM with a button that provides the user with a drop down list of the choice of tags. For example, when the user presses my button on the VM, the user is displayed with a drop down list of a list of tags.

I created the service dialog and button - they work fine.
For one of my Methods I am trying to assign the tags with the following code:

vm = $evm.root['vm']

How would I go on about parsing the data of the selection from the drop down list? Right now with the code above, the VM gets the tag_category_abc/tag_abc assigned to it perfectly fine. Any help with direction to go in would be greatly appreciated.

Hi Ramesh

What element type are you using in the dialog - tag control or drop-down list?