AUTHOR: Marin Bratanov
DATE POSTED: February 05, 2018
The get_clientDataKeyValue() method of the listview returns nothing (undefined) when drag-and-drop is used with client-side data binding.
The drag-and-drop feature is supported with the server-side binding only, and so is the get_clientDataKeyValue() method.
You can use data-* attributes on the items to store the data item, and you can implement a custom drag handle for the items to allow dragging. Note that you must also implement methods that provide the custom handle with the listview ClientID and with the item index.
An example is attached below.