There is a neat Reactive Extension called Buffer:
var o = new ObservableCollection<long>();
var s1 = Observable.Interval(TimeSpan.FromMilliseconds(100)).Subscribe(o.Add);
var s2 =
Observable.FromEventPattern<NotifyCollectionChangedEventArgs>(o, "CollectionChanged")
.Buffer(TimeSpan.FromMilliseconds(500))
.Subscribe(
s =>
{
Console.WriteLine("Last received {0}. Current count: {1}", Convert.ToInt64(s.Last().EventArgs.NewItems[0]), o.Count);
});
This will allow you to receive on collection changed events as they occur, but ignore all except the last one.
UPDATE 1
It is a known issue that CollectionChanged does not fire when items are updated. The MSDN documentation is simply incorrect. You will have to implement a TrulyObservableCollection but your data elements must implement INotifyChanged interface as well.
namespace ConsoleApplication1
{
#region
using System;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Linq;
using System.Reactive.Linq;
using System.Threading;
#endregion
internal class Program
{
#region Methods
private static void Main(string[] args)
{
var autoReset = new AutoResetEvent(false);
var r = new Random();
var o = new TrulyObservableCollection<DataPoint>();
var subscription1 = Observable.Interval(TimeSpan.FromSeconds(1)).Take(3).Subscribe(
i =>
{
o.Add(
new DataPoint
{
ItemCount = r.Next(100)
});
Console.WriteLine("Fire1 {0}", i);
});
var subscription2 =
Observable.FromEventPattern<NotifyCollectionChangedEventArgs>(o, "CollectionChanged")
.Subscribe(s => { Console.WriteLine("List changed. Current total {0}", o.Sum(s1 => s1.ItemCount)); });
var subscription3 = Observable.Interval(TimeSpan.FromSeconds(1)).Delay(TimeSpan.FromSeconds(3)).Take(3).Finally(
() =>
{
o.Clear();
autoReset.Set();
}).Subscribe(
i =>
{
if (o.Any())
{
o[r.Next(o.Count)].ItemCount = r.Next(100);
Console.WriteLine("Fire3 {0}", i);
}
});
autoReset.WaitOne();
}
#endregion
public class TrulyObservableCollection<T> : ObservableCollection<T>
where T : INotifyPropertyChanged
{
#region Constructors and Destructors
public TrulyObservableCollection() { CollectionChanged += this.TrulyObservableCollection_CollectionChanged; }
#endregion
#region Methods
private void TrulyObservableCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.NewItems != null)
{
foreach (Object item in e.NewItems)
{
(item as INotifyPropertyChanged).PropertyChanged += this.item_PropertyChanged;
}
}
if (e.OldItems != null)
{
foreach (Object item in e.OldItems)
{
(item as INotifyPropertyChanged).PropertyChanged -= this.item_PropertyChanged;
}
}
}
private void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
var a = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset);
OnCollectionChanged(a);
}
#endregion
}
private class DataPoint : INotifyPropertyChanged
{
#region Fields
private int itemCount;
#endregion
#region Public Events
public event PropertyChangedEventHandler PropertyChanged;
#endregion
#region Public Properties
public int ItemCount
{
get { return itemCount; }
set
{
itemCount = value;
this.OnPropertyChanged("ItemCount");
}
}
#endregion
#region Methods
protected virtual void OnPropertyChanged(string propertyName = null)
{
var handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
}
}
}
