Datagrid does not maintain sort when the items are updated

Question

I have a nice WPF DataGrid binded to a collection of objects. Everything works fine, when the properties of any object change the grid is updated. The problem is that the rows are not re-sorted when the update happens and then the sort is not valid anymore.

Any idea on how to fix that?

Thanks in advance.

EDIT: This is how I'm binding the DataGrid:

<Controls:DataGrid MinHeight="300" MinWidth="300" ItemsSource="{Binding Data}" AutoGenerateColumns="True">

public class MainWindowViewModel
{ 
    public ObservableCollectionMultiThread<StockViewModel> Data { get; private set; }
} 

public class ObservableCollectionMultiThread<T> : ObservableCollection<T>
{
    // Override the event so this class can access it
    public override event System.Collections.Specialized.NotifyCollectionChangedEventHandler CollectionChanged;

    protected override void OnCollectionChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        // Be nice - use BlockReentrancy like MSDN said
        using (base.BlockReentrancy())
        {
            System.Collections.Specialized.NotifyCollectionChangedEventHandler eventHandler = this.CollectionChanged;
            if (eventHandler == null)
                return;

            Delegate[] delegates = eventHandler.GetInvocationList();
            // Walk thru invocation list
            foreach (System.Collections.Specialized.NotifyCollectionChangedEventHandler handler in delegates)
            {
                DispatcherObject dispatcherObject = handler.Target as DispatcherObject;
                // If the subscriber is a DispatcherObject and different thread
                if (dispatcherObject != null && dispatcherObject.CheckAccess() == false)
                {
                    // Invoke handler in the target dispatcher's thread
                    dispatcherObject.Dispatcher.Invoke(DispatcherPriority.DataBind, handler, this, e);
                }
                else // Execute handler as is
                    handler(this, e);
            }
        }
    }
}

PD: I'm using the DataGrid from CTP October 2008 as I'm with Net 3.5

can you show us how you load and bind the data? you know that depending on the way you do it you should reapply sort criterias? — Davide Piras
Ah, it's my first time with the WPF DataGRid, I didn't know that. I'm using a special ObservableCollection to bind that allows updates from other threads. I'm gonna try with the normal collection and update the question, thanks. — Ignacio Soler Garcia

Ignacio Soler Garcia Ignacio Soler Garcia · Accepted Answer · 2011-09-07T09:12:17

Usually controls on WPF does not respond to item edition. I've used this class as the source for the grid:

using System;
using System.Collections;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Windows.Data;
using System.Windows.Threading;

namespace StockCrawler
{
public class AutoRefreshListCollectionView : ListCollectionView
{

    public AutoRefreshListCollectionView(IList list)
        : base(list)
    {
        this.SubscribeSourceEvents(list, false);
    }

    private void Item_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {

        bool refresh = false;

        foreach (SortDescription sort in this.SortDescriptions)
        {
            if (sort.PropertyName == e.PropertyName)
            {
                refresh = true;
                break;
            }
        }

        if (!refresh)
        {
            foreach (GroupDescription group in this.GroupDescriptions)
            {
                PropertyGroupDescription propertyGroup = group as PropertyGroupDescription;

                if (propertyGroup != null && propertyGroup.PropertyName == e.PropertyName)
                {
                    refresh = true;
                    break;
                }
            }
        }

        if (refresh)
        {
            if (!this.Dispatcher.CheckAccess())
            {
                // Invoke handler in the target dispatcher's thread
                this.Dispatcher.Invoke((Action)this.Refresh); 
            }
            else // Execute handler as is
            {
                this.Refresh();                 
            }
        }
    }

    private void Source_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.Action == NotifyCollectionChangedAction.Add)
        {
            this.SubscribeItemsEvents(e.NewItems, false);
        }
        else if (e.Action == NotifyCollectionChangedAction.Remove)
        {
            this.SubscribeItemsEvents(e.OldItems, true);
        }
        else
        {
            // TODO: Support this

        }
    }

    private void SubscribeItemEvents(object item, bool remove)
    {
        INotifyPropertyChanged notify = item as INotifyPropertyChanged;

        if (notify != null)
        {
            if (remove)
            {
                notify.PropertyChanged -= this.Item_PropertyChanged;
            }
            else
            {
                notify.PropertyChanged += this.Item_PropertyChanged;
            }
        }
    }

    private void SubscribeItemsEvents(IEnumerable items, bool remove)
    {
        foreach (object item in items)
        {
            this.SubscribeItemEvents(item, remove);
        }
    }

    private void SubscribeSourceEvents(object source, bool remove)
    {
        INotifyCollectionChanged notify = source as INotifyCollectionChanged;

        if (notify != null)
        {
            if (remove)
            {
                notify.CollectionChanged -= this.Source_CollectionChanged;
            }
            else
            {
                notify.CollectionChanged += this.Source_CollectionChanged;
            }
        }

        this.SubscribeItemsEvents((IEnumerable)source, remove);
    }
}
}

Datagrid does not maintain sort when the items are updated

1 Answers