public static DisposableReadOnlyObservableCollection <TResult> MakeOneWayLinkedCollectionMany <TSource, TCollection, TResult>(this TCollection source, Func <TSource, IEnumerable <TResult> > selector)
where TCollection : INotifyCollectionChanged, IEnumerable <TSource>
{
List <int> counts = new List <int>();
var ret = new DisposableObservableCollection <TResult>(source.Select(selector).SelectMany(x => { counts.Add(x?.Count() ?? 0); return(x ?? new TResult[0]); }));
ret.AddDisposable(source.ObserveCollectionChanged <TCollection, TSource>((item, index) =>
{
int idx = counts.Take(index).Sum();
int lastIdx = idx;
foreach (var newItem in selector(item) ?? new TResult[0])
{
ret.Insert(lastIdx++, newItem);
}
counts.Insert(index, lastIdx - idx);
}, (item, index) =>
{
int idx = counts.Take(index).Sum();
int lastIdx = idx + counts[index];
for (; idx < lastIdx; idx++)
{
ret.RemoveAt(idx);
}
counts.RemoveAt(index);
}, () =>
{
counts.Clear();
ret.Clear();
ret.AddRange(source.Select(selector).SelectMany(x => { counts.Add(x?.Count() ?? 0); return(x ?? new TResult[0]); }));
}));
return(new DisposableReadOnlyObservableCollection <TResult>(ret));
}
public static DisposableReadOnlyObservableCollection <TSource> ObservableConcat <TSource, TCollection>(this TCollection first, IEnumerable <TSource> second)
where TCollection : INotifyCollectionChanged, IEnumerable <TSource>
{
var ret = new DisposableObservableCollection <TSource>(first.Concat(second));
ret.AddDisposable(first.ObserveCollectionChanged <TCollection, TSource>((item, index) =>
ret.Insert(index, item)
, (item, index) =>
ret.RemoveAt(index)
, () =>
{
ret.Clear();
ret.AddRange(first.Concat(second));
}));
return(new DisposableReadOnlyObservableCollection <TSource>(ret));
}
public static DisposableReadOnlyObservableCollection <TResult> MakeOneWayLinkedCollection <TSource, TCollection, TResult>(this TCollection source, Func <TSource, TResult> selector)
where TCollection : INotifyCollectionChanged, IEnumerable <TSource>
{
var ret = new DisposableObservableCollection <TResult>(source.Select(selector));
ret.AddDisposable(source.ObserveCollectionChanged <TCollection, TSource>((item, index) =>
{
ret.Insert(index, selector(item));
}, (item, index) =>
{
ret.RemoveAt(index);
}, () =>
{
ret.Clear();
ret.AddRange(source.Select(selector));
}));
return(new DisposableReadOnlyObservableCollection <TResult>(ret));
}