private void Legend_Refreshed(object sender, ESRI.ArcGIS.Client.Toolkit.Legend.RefreshedEventArgs e)
{
var items = e.LayerItem.LegendItems;
if (e.LayerItem.Layer is FeatureLayer && items != null)
{
// Group the items by Label and keep only the first one
var toRemove = items.GroupBy(item => item.Label).SelectMany(g => g.Skip(1)).ToArray();
foreach (var item in toRemove)
items.Remove(item);
}
}