2 Issues - Cannot get DispatcherObject from WeakEvent.WeakListener and Cannot Insert Row when list is empty

[Rick]

I am currently having 2 issues with the RadGridView

1)
I am receiving calls from a WCF Service in the client that do the usual CRUD actions.  Of course this comes in on a different thread than the UI thread.  So I have a dispatchable observable collection with the code below.

    using System;
    using System.Collections.Generic;
    using System.Collections.ObjectModel;
    using System.Collections.Specialized;
    using System.Windows.Threading;
 
    public class DispatchableObservableCollection<T>
        : ObservableCollection<T>
    {
        public DispatchableObservableCollection()
        {
        }
 
        public DispatchableObservableCollection(IEnumerable<T> collection)
            : base(collection)
        {
        }
 
        // Override the event so this class can access it
        public override event NotifyCollectionChangedEventHandler CollectionChanged;
 
        protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            // Be nice - use BlockReentrancy like MSDN said
            using (BlockReentrancy())
            {
                NotifyCollectionChangedEventHandler eventHandler = CollectionChanged;
                if (eventHandler != null)
                {
                    Delegate[] delegates = eventHandler.GetInvocationList();
                    // Walk thru invocation list
                    foreach (NotifyCollectionChangedEventHandler handler in delegates)
                    {
                        DispatcherObject dispatcherObject = handler.Target as DispatcherObject;
                        // If the subscriber is a DispatcherObject and different thread
                        if (dispatcherObject != null
                            && !dispatcherObject.CheckAccess())
                        {
                            // Invoke handler in the target dispatcher's thread
                            dispatcherObject.Dispatcher.Invoke(DispatcherPriority.DataBind,
                                                               handler,
                                                               this,
                                                               e);
                        }
                        else // Execute handler as is
                        {
                            handler(this,
                                    e);
                        }
                    }
                }
            }
        }
    }

The problem is the object subscribed to NotifyCollectionChanged event for the grid  is WeakEvent.WeakListener and the cast to DispatcherObject fails (null).   How do I get the DispatcherObject from handler.Target.  I'm trying to make this work so that I don't have to use Application.Current.Dispatcher as a bail out so that it will work for UI objects not on the primary UI thread.  Is there a work around?


2)

I have detected some odd behavior for add new item.  If I have a grid and remove all items and then want to add more back into the grid it works fine.  However, if I remove all items from the collection and then close the application and restart when I click the add new item header nothing happens.  i.e.,  a new row is not added.  The collection I am using is the one above and the collection is there (Not null), it is just empty.  Thoughts?


Thanks for the help,

Rick
 

[Tarik]

Hi,

I have the same first issue as explained by Rick, plz is there any solution for it ?

regards.

[Ivan Ivanov]

Hello Tarik,

Do you have a valid subscriber for the event that is a DispatcherObject? I prepared a dummy sample project that illustrates how to implement it.

Regards,
Ivan Ivanov
Telerik