A bool indicating whether or not to separate pushpin icons that are close to each other on the map so that they are more visible. Optional. The default value is false. Set this property before making a service request.
public bool PreventIconCollision { set; get; }
If the PreventIconCollision property is set to true, then overlapping pushpin icons are separated and each pushpin is drawn on the map where there is more space. Additionally, a line is drawn from the new pushpin to the location on the map where the pushpin would have originally been placed. This pushpin display style is referred to as "icon on a stick."
If the PreventIconCollision property is set to true, then only pushpin icons with the following Pushpin.IconStyle Property values are affected: 13, 14, 15, and 16.
Reference
MapUriRequest.Pushpins Property