OK, so it's a known problem. We had our own implementation of IBindingList before switching to BindingList<T>, but as you say the event notification is tricky to get right.
Is there any good in-depth documentation of how the data binding protocol is supposed to work, especially using DataGrid and DataGridView? Sometimes in the MSDN documentation it feels like "DataSet supports data binding. If you have custom collection and classes here are the interfaces we use... good luck...". But then again adding 10000 objects is not something you would do when working in a grid so maybe we are trying add too much responsibility to a single typed collection class... what's you strategies for custom business object collections? // Kristofer -----Original Message----- From: Discussion of advanced .NET topics. [mailto:[EMAIL PROTECTED] On Behalf Of gregory young Sent: den 31 oktober 2006 17:07 To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM Subject: Re: [ADVANCED-DOTNET] BindingList<T>.AddNew performance problem What we did to work around this was implement IBindingList on our own using a hashlist .. you could also fairly easily override the behavior to index your list in a derived class by overriding add/remove/etc (note that if you go this route you will need to get out reflector to make sure you raise the proper events etc and its a bad overall design). Cheers, Greg On 10/31/06, Krebs Kristofer <[EMAIL PROTECTED]> wrote: > Hi! > > I found a weird thing while I was investigating a performance issue. We > use BindningList<T> as base class for our business object collections. > It seems that BindingList<T>.AddNew calls IndexOf(T item) (which has to > iterate and do Equals for all items in the collection to find it... it's > probably last) after the call to AddNewCore IF the item (of T) overrides > Equals or implements IEquatable<T>. This makes adding new items this way > go slower and slower. Adding object via the usual Add does not cause > this problem. > > So, my question is why, and how can I avoid this behaviour? I any case; > beware of this... > > Test code ("dry coded"): > > TestEntityCollection coll = new TestEntityCollection(); > > // Takes forever on my machine i.e. at least 25 seconds.... > for (int i = 0; i < 10000; i++) { > TestEntity obj = coll.AddNew(); > obj.Name = "Name" + i; > } > > // This is much faster, < 0.5 seconds > for (int i = 0; i < 10000; i++) { > TestEntity obj = new TestEntity(); > obj.ID = Guid.NewGuid(); > obj.Name = "Name" + i; > coll.Add(obj); > } > .... > > public class TestEntity : IEquatable<TestEntity> > { > private Guid _id; > private string _name; > > > public Guid ID { get { return _id; } set { _id = value; } } > public string Name { get { return _name; } set { _name = value; } > > > // This causes bad performance on AddNew it seems, remove > IEquatable > // implementation to see the difference. Overriding Equals(object) > // causes the same thing > public bool Equals(TestEntity other) { > return ((object)other != null && this.ID.Equals(other.ID); > } > } > > public class TestEntityCollection : BindingList<TestEntity> > { > public override object AddNewCore() { > TestEntity item = new TestEntity(); > item.ID = Guid.NewGuid(); // Just an example of id initialization > Add(item); > return item; > } > } > > =================================== > This list is hosted by DevelopMentor(r) http://www.develop.com > > View archives and manage your subscription(s) at http://discuss.develop.com > -- If knowledge can create problems, it is not through ignorance that we can solve them. Isaac Asimov =================================== This list is hosted by DevelopMentor(r) http://www.develop.com View archives and manage your subscription(s) at http://discuss.develop.com =================================== This list is hosted by DevelopMentor® http://www.develop.com View archives and manage your subscription(s) at http://discuss.develop.com
