This will work if you define pages and classes for Data Page as well as shown below.
D_ApplicationType to be mapped to 'Code-Pega-List' page.
D_ApplicationType.pxResults to be mapped to "MHBK-GenAppFW-Data-GAApplicationType".
And you set the properties like this.
D_ApplicationType.pxResults(1).ID = ""
When using .pxResults(1).ID this was not working, because the .pxResults property is mapped to '$CLASS'. you can verify this in ".pxResults" property definition. Since in the primary page context, .pxResults is still pointing to '$CLASS', regardless of the page value set in the pages and classes tab.