How to retrieve last level data from Client Dashboard Item and display it using different ASP.NET controls

This solution can be used with both ASPxDashboardViewer and MVCxDashboardViewer controls:
To request data displayed in the specific Dashboard Item, you should call GetItemData methods of the ASPxClientDashboardViewer object. 
Then, you need to iterate through the item's elements (rows, cells, points, etc ), collect information about corresponding dimensions and measures and store it as JSON collection. You can send this collection to the server in a string format using the JSON.stringify Function. To parse the string on the server, you can use the Json.Decode Method. 

Note that the Pivot Item returns last level data only for completely expanded rows and columns.
See Also:
T182186: How to get visible data from a certain dashboard item on the client side and process it on the server side
T148767: How to obtain a dashboard item's client data in the Web Viewer