public IList<DisplayUnitFormat> GetAvailableElevationUnitFormats()

{
    //If the map is not a scene, the list of current
    //Project distance units will be returned
    //Note: Must be on the QueuedTask.Run()
    var elev_units = map.GetAvailableElevationUnitFormats();
}

{
    //Trying to set the elevation unit on a map other than
    //a scene will throw an InvalidOperationException
    if (map.IsScene)
    {
        //Get the list of available elevation unit formats
        //for the current map
        var loc_units = map.GetAvailableElevationUnitFormats();
        //arbitrarily use the last unit in the list
        //Note: Must be on the QueuedTask.Run()
        map.SetElevationUnitFormat(loc_units.Last());
    }
}