I'd like to apologize for the misleading information from my previous post.
The behavior that you are trying to achieve is just not supported by our RadListPicker and RadContextMenu implementations, as it doesn't follow the expected behavior in Windows Phone. The ListPicker control as a concept, is allowing the user to choose an item among the items in the provided list and doesn't provide options for editing the collection. Both RadListPicker and RadContextMenu are supposed to open after the gesture is completed, and as you can see they follow their expected behavior. You can think about modifying your scenario so that these controls are not used simultaneously. For example, the items can reside in RadDataBoundListBox, instead of RadListPicker.
I hope this information helps and once again apologies for the misunderstanding.
the Telerik team
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