How can I make a read-only ObservableCollection property?

Question

I\'d like to expose a property on a view model that contains a list of objects (from database).

I need this collection to be read-only. That is, I want to prevent A

Answer 1

I don't like using ReadOnlyObservableCollection 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 
       : ICollection, 
         INotifyCollectionChanged
{}

public interface IReadOnlyNotifyCollection 
       : IReadOnlyCollection, 
         INotifyCollectionChanged
{}

public class NotifyCollection 
       : ObservableCollection, 
         INotifyCollection, 
         IReadOnlyNotifyCollection
{}

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


        //Covarience
        var readOnlyListWithChanges = 
            new List>()
                {
                    new NotifyCollection