public bool Equals(ObservableGroupingView <TKey, TElement> x, ObservableGroupingView <TKey, TElement> y)
 {
     if (x != null && y != null)
     {
         return(keyComparer.Equals(x.Key, y.Key));
     }
     if (x == null && y == null)
     {
         return(true);
     }
     return(false);
 }
 public int GetHashCode(ObservableGroupingView <TKey, TElement> obj)
 {
     return(obj == null ? 0 : keyComparer.GetHashCode(obj.Key));
 }