The feature is implemented indeed, but after some discussions we decided to call the property Position. It reflects the relative order of a tile within a TileView control, but note that it's different from an object's Index within a TileView's Items collection. This approach works for most practical purposes and reordering the tiles via dragging changes a tile's Position, but not it's Index in the Items collection. There is also an event that is fired whenever a tile changes its Position.
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