ObservableCollection(Of T) vs BindingList(Of T)?

问题:

I've developped some data based Winforms Application this last two years and all works fine. This application are built on layers (DataAccess, Business Logic and UI). For the Businness Logic, all my objects inherit from a base class called BaseEntity with the following definition (there are some custom objects and interfaces, combined with framework elements) :

Public MustInherit Class BaseEntity
    Inherits SerializableObject
    Implements IEntity
    Implements IComparer,  _
               IEditableObject,  _
               INotifyPropertyChanging, INotifyPropertyChanged,  _
               IApplicationSecurity
  End Class

In the same core library, I have a generic base collection BaseEntityCollection. These collection allows me to define, for each object, his related strongly typed collection, wich is very interresting, in data based applications. Here is it's base definition :

 Public MustInherit Class BaseEntityCollection(Of T As BaseEntity)
    Inherits BindingList(Of T)
    Implements IEntityCollection
    Implements INotifyPropertyChanged, INotifyPropertyChanging, ICopyable(Of T)
    Implements IDisposable
    Implements ISerializable
  End Class

As you can see, I use all the stuff that's needed for correct databinding in Winforms :

• INotifyPropertyChanged,INotifyPropertyChanging, IEditableObject for the object.
• A collection based on BindingList(Of T) for my collection.

I'm also interrested on new technologies, so I recently watched some webcast about WPF. In these webcast, they use as base class for collection and databinding support ObservableCollection(Of T).

I'm thinking on migrate some of my applications from Winforms to WPF for the UI Layer.

My question is, for my business logic, is it better keep my collections based on BindingList(Of T) or should I change my base collection class to make it inherit from ObservableCollection(Of T). I would like to keep a unique base collection for all my projects, that can be used as well in Winforms Applications, WPF Application or ASP.NET. I'm also using Linq to Objects in my projects, so I don't have restriction by keeping my projects based on only framework 2.0.

Thanks,

ClaBer

回答1:

Claber,

I would keep the BindingList, because BindingList supports more interfaces and more feature rich than ObservableCollection. For example:

1. BindingList implements IList of T, whereas ObservableCollection does not.
2. BindingList implements ICancelAddNew interface that data binding mechanisms uses for cancelling the newly added item (when you clicked escape after adding a row to DataGridView, the row will dissappear).

I'm very new to WPF myself, and don't know the specific advantages ObservableCollection offers.

Hope this helps.

回答2:

I think your answer lies in there : http://xceed.com/CS/blogs/dontpanic/archive/2009/04/01/i-notify-we-notify-we-all-wait-no-we-don-t.aspx

To be short, ObservableCollection does not listen to changes in its children but only to Insert and Remove events.

On the other side BindingList does listen to changes and updates raised by its children. But because Binding list must listen to all its children to propagate the change notifications, it results in more memory load.

Hope this will help :)

--Bruno

回答3:

Adding my two cents to an older topic:

When data binding either of these generic collections to a WinForms DataGridView and then updating properties in the source data for multiple selected rows, you'll see:

1. The ObservableCollection<T> will only update the cell values of the most recently selected row.
2. The BindingList<T> will update the cell values of all the selected rows.

I think they each have their advantages and disadvantages, but the above example can be a gotcha for those who are unaware of it.