If you search for Windows Phone 8.1 Context Menu, you’ll likely be riddled with Silverlight solutions, just as I did. Luckily, since Windows Phone 8.1 WinRT shares many components of Windows 8, using a context menu on your list data is quite simple, provided you know how to search for it. I was lucky to stumble upon the Menu Flyout so I’m here to share my finding.
MSDN has a great example on Menu Flyouts. A menu flyout in Windows 8 is a simple popup menu relative to the control the user is interacting with. On Windows Phone 8.1, this MenuFlyout control will be displayed as a full width popup, mimicking the context menu known to Windows Phone. Head over to MSDN to see the example.
Hope this helps.