Read only observable collection

Question

I have my class that has an internal observable collection. I want to pass the data in this to a user of the class via a function.

I don't want them to be able to change the objects inside of the observable collection or the collection itself.

What is the best way to do this performance and ease of use wise?

score 5 · Accepted Answer · answered May 19 '10 at 18:23

5

Probably using this: ReadOnlyObservableCollection<T>. Note that you will have to write your own read-only wrappers for your objects, since the ReadOnlyObservableCollection<T> only prevents updates to the collection itself.

answered May 19 '10 at 18:23

Stephen Cleary

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score 2 · Answer 2 · answered Mar 18 '13 at 10:17

I don't like using ReadOnlyObservableCollection<T> as it seems like a mistake / broken class; I prefer a contract based approach instead.

Here is what I use that allows for covarience:

public interface INotifyCollection<T> : ICollection<T>, INotifyCollectionChanged
{
}

public interface IReadOnlyNotifyCollection<out T> : IReadOnlyCollection<T>, INotifyCollectionChanged
{
}

public class NotifyCollection<T> : ObservableCollection<T>, INotifyCollection<T>, IReadOnlyNotifyCollection<T>
{
}

public class Program
{
    private static void Main(string[] args)
    {
        var full = new NotifyCollection<string>();
        var readOnlyAccess = (IReadOnlyCollection<string>) full;
        var readOnlyNotifyOfChange1 = (IReadOnlyNotifyCollection<string>) full;

        //Covarience
        var readOnlyListWithChanges = new List<IReadOnlyNotifyCollection<object>>()
            {
                new NotifyCollection<object>(),
                new NotifyCollection<string>(),
            };
    }
}

Wow, what a nice approach. Thank you for sharing. – PavelS Jul 09 '18 at 22:45 — PavelS, Jul 09 '18 at 22:45

score 1 · Answer 3 · answered Aug 10 '11 at 12:53

What I did for this type of Implementation was to have a shared class with an underlying BindingList, for the entire client side to use. There was a public readonly getter, and in the actual UI presenter I included a type of Filtered List (Bound to the underlying singleton on instantiation) that would allow the client view to apply an Expression filter (LINQ Enabled too, based on underlying T) and, with the UI controls databound to this filtered list, list changes would automatically support UI Update only if it passed filter. And it was readonly, because the server side was publishing updates to an overall WCF controller class that passed them down to the List layer, skipping the UI entirely.

Welcome to Stackoverflow and congrats to your first answer. Please try to make it easier to understand - e.g. by formatting (Code, seperate paragraphs or list styles). Maybe an example would help? — Mateng, Nov 14 '12 at 23:02

Read only observable collection

3 Answers3