Fixed the caching issue that causes mails to be not removed. Improved drag/drop.

Wino.Core.Domain/Translations/en_US/resources.json

@@ -484,6 +484,7 @@
     "MailOperation_Unarchive": "Unarchive",
     "MailOperation_ViewMessageSource": "View message source",
     "MailOperation_Zoom": "Zoom",
+    "MailsDragging": "Dragging {0} item(s)",
     "MailsSelected": "{0} item(s) selected",
     "MarkFlagUnflag": "Mark as flagged/unflagged",
     "MarkReadUnread": "Mark as read/unread",

Wino.Mail.ViewModels/Collections/WinoMailCollection.cs

@@ -233,6 +233,11 @@ public class WinoMailCollection : ObservableRecipient, IRecipient<SelectedItemsC
         return !string.IsNullOrEmpty(threadId) && _threadIdToItemsMap.ContainsKey(threadId);
     }
 
+    /// <summary>
+    /// Checks whether a mail with the given UniqueId currently exists in this collection.
+    /// </summary>
+    public bool ContainsMailUniqueId(Guid uniqueId) => MailCopyIdHashSet.ContainsKey(uniqueId);
+
     /// <summary>
     /// Finds a MailItemViewModel by its UniqueId, searching through all items including those inside threads.
     /// </summary>
@@ -443,10 +448,17 @@ public class WinoMailCollection : ObservableRecipient, IRecipient<SelectedItemsC
     {
         // Try cache first
         if (_itemToGroupMap.TryGetValue(item, out var cachedGroup))
+        {
+            // Cache can become stale during concurrent list refreshes/moves.
+            // Validate before returning so we don't mutate a detached group.
+            if (_mailItemSource.Contains(cachedGroup) && cachedGroup.Contains(item))
             {
                 return cachedGroup;
             }
 
+            _itemToGroupMap.TryRemove(item, out _);
+        }
+
         // Fallback to search if not in cache
         foreach (var group in _mailItemSource)
         {
@@ -487,6 +499,8 @@ public class WinoMailCollection : ObservableRecipient, IRecipient<SelectedItemsC
         {
             MailCopyIdHashSet.Clear();
             _threadIdToItemsMap.Clear();
+            _itemToGroupMap.Clear();
+            _uniqueIdToMailItemMap.Clear();
             _uniqueIdToThreadMap.Clear();
         }
 
@@ -741,9 +755,6 @@ public class WinoMailCollection : ObservableRecipient, IRecipient<SelectedItemsC
     /// <returns></returns>
     public Task UpdateMailCopy(MailCopy updatedMailCopy, MailUpdateSource mailUpdateSource)
     {
-        // This item doesn't exist in the list.
-        if (!MailCopyIdHashSet.ContainsKey(updatedMailCopy.UniqueId)) return Task.CompletedTask;
-
         return ExecuteUIThread(() =>
         {
             var itemContainer = GetMailItemContainer(updatedMailCopy.UniqueId);
@@ -762,6 +773,12 @@ public class WinoMailCollection : ObservableRecipient, IRecipient<SelectedItemsC
                 itemContainer.ItemViewModel.IsBusy = mailUpdateSource == MailUpdateSource.ClientUpdated;
 
                 UpdateUniqueIdHashes(itemContainer.ItemViewModel, true);
+
+                // Keep thread membership cache in sync for items rendered inside thread containers.
+                if (itemContainer.ThreadViewModel != null)
+                {
+                    _uniqueIdToThreadMap[itemContainer.ItemViewModel.MailCopy.UniqueId] = itemContainer.ThreadViewModel;
+                }
             }
 
             // Trigger thread property notifications if this item is in a thread
@@ -836,17 +853,19 @@ public class WinoMailCollection : ObservableRecipient, IRecipient<SelectedItemsC
 
     public async Task RemoveAsync(MailCopy removeItem)
     {
-        // This item doesn't exist in the list.
-        if (!MailCopyIdHashSet.ContainsKey(removeItem.UniqueId)) return;
+        var itemContainer = GetMailItemContainer(removeItem.UniqueId);
 
-        if (_uniqueIdToThreadMap.TryGetValue(removeItem.UniqueId, out var threadMailItemViewModel))
+        // This item doesn't exist in the list.
+        if (itemContainer?.ItemViewModel == null) return;
+
+        if (itemContainer.ThreadViewModel != null)
         {
             // Item is inside a thread - use cached lookups instead of scanning all groups.
+            var threadMailItemViewModel = itemContainer.ThreadViewModel;
             var group = FindGroupContainingItem(threadMailItemViewModel);
             if (group == null) return;
 
-            var removalItem = threadMailItemViewModel.ThreadEmails.FirstOrDefault(e => e.MailCopy.UniqueId == removeItem.UniqueId);
-            if (removalItem == null) return;
+            var removalItem = itemContainer.ItemViewModel;
 
             // Update ThreadId cache before modifying the thread
             UpdateThreadIdCache(threadMailItemViewModel, false);
@@ -889,36 +908,11 @@ public class WinoMailCollection : ObservableRecipient, IRecipient<SelectedItemsC
         }
         else
         {
-            // Standalone item - use cached lookup.
-            IMailListItem mailItem = null;
-            ObservableGroup<object, IMailListItem> group = null;
+            // Standalone item.
+            IMailListItem mailItem = itemContainer.ItemViewModel;
+            var group = FindGroupContainingItem(mailItem);
 
-            if (_uniqueIdToMailItemMap.TryGetValue(removeItem.UniqueId, out var cachedItem))
-            {
-                mailItem = cachedItem;
-                group = FindGroupContainingItem(mailItem);
-            }
-
-            // Fallback to scan if not in cache
-            if (mailItem == null || group == null)
-            {
-                for (int i = 0; i < _mailItemSource.Count; i++)
-                {
-                    var g = _mailItemSource[i];
-                    for (int k = 0; k < g.Count; k++)
-                    {
-                        if (g[k] is MailItemViewModel mvm && mvm.MailCopy.UniqueId == removeItem.UniqueId)
-                        {
-                            mailItem = mvm;
-                            group = g;
-                            break;
-                        }
-                    }
-                    if (mailItem != null) break;
-                }
-            }
-
-            if (mailItem != null && group != null)
+            if (group != null)
             {
                 await RemoveItemInternalAsync(group, mailItem);
             }

Wino.Mail.ViewModels/MailListPageViewModel.cs

@@ -99,6 +99,16 @@ public partial class MailListPageViewModel : MailBaseViewModel,
     [ObservableProperty]
     private bool isMultiSelectionModeEnabled;
 
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(SelectedMessageText))]
+    [NotifyPropertyChangedFor(nameof(DraggingMessageText))]
+    public partial bool IsDragInProgress { get; set; }
+
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(SelectedMessageText))]
+    [NotifyPropertyChangedFor(nameof(DraggingMessageText))]
+    public partial int DraggingItemsCount { get; set; }
+
     [ObservableProperty]
     public partial string SearchQuery { get; set; }
 
@@ -291,7 +301,13 @@ public partial class MailListPageViewModel : MailBaseViewModel,
     public bool IsFolderSynchronizationEnabled => ActiveFolder?.IsSynchronizationEnabled ?? false;
     public bool IsArchiveSpecialFolder => ActiveFolder?.SpecialFolderType == SpecialFolderType.Archive;
 
-    public string SelectedMessageText => MailCollection.SelectedItemsCount > 0 ? string.Format(Translator.MailsSelected, MailCollection.SelectedItemsCount) : Translator.NoMailSelected;
+    public string SelectedMessageText => IsDragInProgress
+        ? string.Format(Translator.MailsDragging, DraggingItemsCount)
+        : MailCollection.SelectedItemsCount > 0
+            ? string.Format(Translator.MailsSelected, MailCollection.SelectedItemsCount)
+            : Translator.NoMailSelected;
+
+    public string DraggingMessageText => string.Format(Translator.MailsDragging, DraggingItemsCount);
 
     /// <summary>
     /// Indicates current state of the mail list. Doesn't matter it's loading or no.
@@ -361,6 +377,12 @@ public partial class MailListPageViewModel : MailBaseViewModel,
         SelectedFolderPivot?.SelectedItemCount = MailCollection.SelectedItemsCount;
     }
 
+    public void SetDragState(bool isDragInProgress, int draggingItemsCount = 0)
+    {
+        IsDragInProgress = isDragInProgress;
+        DraggingItemsCount = isDragInProgress ? Math.Max(1, draggingItemsCount) : 0;
+    }
+
     private void NotifyItemFoundState()
     {
         OnPropertyChanged(nameof(IsEmpty));
@@ -718,7 +740,15 @@ public partial class MailListPageViewModel : MailBaseViewModel,
     {
         base.OnMailUpdated(updatedMail, source);
 
+        try
+        {
+            await listManipulationSemepahore.WaitAsync();
             await MailCollection.UpdateMailCopy(updatedMail, source);
+        }
+        finally
+        {
+            listManipulationSemepahore.Release();
+        }
 
         // await ExecuteUIThread(() => { SetupTopBarActions(); });
     }
@@ -727,22 +757,21 @@ public partial class MailListPageViewModel : MailBaseViewModel,
     {
         base.OnMailRemoved(removedMail);
 
-        if (removedMail.AssignedAccount == null || removedMail.AssignedFolder == null) return;
+        if (removedMail.AssignedAccount == null) return;
 
-        // We should delete the items only if:
-        // 1. They are deleted from the active folder.
-        // 2. Deleted from draft or sent folder.
-        // 3. Removal is not caused by Gmail Unread folder action.
-        // Delete/sent are special folders that can list their items in other folders.
+        try
+        {
+            await listManipulationSemepahore.WaitAsync();
 
-        bool removedFromActiveFolder = ActiveFolder.HandlingFolders.Any(a => a.Id == removedMail.AssignedFolder.Id);
-        bool removedFromDraftOrSent = removedMail.AssignedFolder.SpecialFolderType == SpecialFolderType.Draft ||
-                                      removedMail.AssignedFolder.SpecialFolderType == SpecialFolderType.Sent;
+            // Remove only if this specific mail copy currently exists in this list.
+            // Using AssignedFolder-based checks is unreliable for move flows because the
+            // same MailCopy instance can be updated before this message is handled.
+            bool removedItemExistsInCurrentList = MailCollection.ContainsMailUniqueId(removedMail.UniqueId);
 
-        bool isDeletedByGmailUnreadFolderAction = ActiveFolder.SpecialFolderType == SpecialFolderType.Unread &&
+            bool isDeletedByGmailUnreadFolderAction = ActiveFolder?.SpecialFolderType == SpecialFolderType.Unread &&
                                                       gmailUnreadFolderMarkedAsReadUniqueIds.Contains(removedMail.UniqueId);
 
-        if ((removedFromActiveFolder || removedFromDraftOrSent) && !isDeletedByGmailUnreadFolderAction)
+            if (removedItemExistsInCurrentList && !isDeletedByGmailUnreadFolderAction)
             {
                 bool isDeletedMailSelected = MailCollection.SelectedItems.Any(a => a.MailCopy.UniqueId == removedMail.UniqueId);
 
@@ -779,6 +808,11 @@ public partial class MailListPageViewModel : MailBaseViewModel,
                 gmailUnreadFolderMarkedAsReadUniqueIds.Remove(removedMail.UniqueId);
             }
         }
+        finally
+        {
+            listManipulationSemepahore.Release();
+        }
+    }
 
     protected override async void OnFolderDeleted(MailItemFolder folder)
     {

Wino.Mail.WinUI/Controls/ListView/WinoListView.cs

@@ -1,10 +1,12 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using System.Windows.Input;
 using CommunityToolkit.WinUI;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
+using Wino.Core.Domain;
 using Wino.Core.Domain.Models.MailItem;
 using Wino.Mail.ViewModels.Data;
 
@@ -21,12 +23,16 @@ public partial class WinoListView : Microsoft.UI.Xaml.Controls.ListView
     [GeneratedDependencyProperty]
     public partial ICommand? LoadMoreCommand { get; set; }
 
+    public event EventHandler<MailDragStateChangedEventArgs>? MailDragStateChanged;
+
     protected override void OnApplyTemplate()
     {
         base.OnApplyTemplate();
 
-        DragItemsStarting += ItemDragStarting;
         DragItemsStarting -= ItemDragStarting;
+        DragItemsStarting += ItemDragStarting;
+        DragItemsCompleted -= ItemDragCompleted;
+        DragItemsCompleted += ItemDragCompleted;
 
         internalScrollviewer = GetTemplateChild(PART_ScrollViewer) as ScrollViewer;
 
@@ -222,6 +228,7 @@ public partial class WinoListView : Microsoft.UI.Xaml.Controls.ListView
     public void Cleanup()
     {
         DragItemsStarting -= ItemDragStarting;
+        DragItemsCompleted -= ItemDragCompleted;
 
         if (internalScrollviewer != null)
         {
@@ -236,20 +243,99 @@ public partial class WinoListView : Microsoft.UI.Xaml.Controls.ListView
         // Meaning that if users drag 1 mail from Account A/Inbox and 1 mail from Account B/Inbox,
         // and drop to Account A/Inbox, the mail from Account B/Inbox will NOT be moved.
 
+        var itemsToDrag = ResolveDraggedMailItems(args);
+
+        if (itemsToDrag.Count == 0)
+        {
+            return;
+        }
+
+        var dragPackage = new MailDragPackage(itemsToDrag.Cast<object>());
+        args.Data.Properties.Add(nameof(MailDragPackage), dragPackage);
+
+        var draggingText = string.Format(Translator.MailsDragging, itemsToDrag.Count);
+        args.Data.SetText(draggingText);
+        args.Data.Properties.Title = draggingText;
+        // args.DragUI.SetContentFromDataPackage();
+
+        MailDragStateChanged?.Invoke(this, new MailDragStateChangedEventArgs(true, itemsToDrag.Count));
+    }
+
+    private void ItemDragCompleted(ListViewBase sender, DragItemsCompletedEventArgs args)
+    {
+        MailDragStateChanged?.Invoke(this, new MailDragStateChangedEventArgs(false, 0));
+    }
+
+    private List<MailItemViewModel> ResolveDraggedMailItems(DragItemsStartingEventArgs args)
+    {
+        var draggedItems = ExpandDragItems(args.Items.Cast<object>());
+        var selectedItems = GetSelectedMailItemsFromCurrentList();
+
+        if (selectedItems.Count > 1)
+        {
+            var selectedIds = selectedItems.Select(a => a.UniqueId).ToHashSet();
+            bool dragStartedFromSelection = draggedItems.Any(a => selectedIds.Contains(a.UniqueId));
+
+            if (dragStartedFromSelection)
+            {
+                return selectedItems;
+            }
+        }
+
+        return draggedItems.Count > 0 ? draggedItems : selectedItems;
+    }
+
+    private List<MailItemViewModel> GetSelectedMailItemsFromCurrentList()
+    {
         if (IsThreadListView)
         {
-            var allItems = args.Items.Cast<MailItemViewModel>();
-
-            // Set native drag arg properties.
-            var dragPackage = new MailDragPackage(allItems.Cast<IMailListItem>());
-
-            args.Data.Properties.Add(nameof(MailDragPackage), dragPackage);
+            return Items
+                .Cast<object>()
+                .OfType<MailItemViewModel>()
+                .Where(a => a.IsSelected)
+                .GroupBy(a => a.UniqueId)
+                .Select(a => a.First())
+                .ToList();
         }
-        else
+
+        return Items
+            .Cast<object>()
+            .OfType<IMailListItem>()
+            .SelectMany(a => a.GetSelectedMailItems())
+            .GroupBy(a => a.UniqueId)
+            .Select(a => a.First())
+            .ToList();
+    }
+
+    private static List<MailItemViewModel> ExpandDragItems(IEnumerable<object> dragItems)
     {
-            var dragPackage = new MailDragPackage(args.Items.Cast<IMailListItem>());
+        var result = new List<MailItemViewModel>();
 
-            args.Data.Properties.Add(nameof(MailDragPackage), dragPackage);
+        foreach (var dragItem in dragItems)
+        {
+            if (dragItem is MailItemViewModel mailItem)
+            {
+                result.Add(mailItem);
             }
+            else if (dragItem is ThreadMailItemViewModel threadItem)
+            {
+                result.AddRange(threadItem.ThreadEmails);
+            }
+            else if (dragItem is IMailListItem mailListItem)
+            {
+                result.AddRange(mailListItem.GetSelectedMailItems());
+            }
+        }
+
+        return result
+            .GroupBy(a => a.UniqueId)
+            .Select(a => a.First())
+            .ToList();
     }
 }
+
+public sealed class MailDragStateChangedEventArgs(bool isDragging, int draggedItemCount) : EventArgs
+{
+    public bool IsDragging { get; } = isDragging;
+    public int DraggedItemCount { get; } = draggedItemCount;
+}

Wino.Mail.WinUI/Controls/WinoExpander.cs

@@ -62,7 +62,7 @@ public partial class WinoExpander : Control
         clipComposition.Clip = clipComposition.Compositor.CreateInsetClip();
 
         ContentAreaWrapper.SizeChanged += ContentSizeChanged;
-        HeaderGrid.Tapped += HeaderTapped;
+
     }
 
     private void ContentSizeChanged(object sender, SizeChangedEventArgs e)
@@ -71,21 +71,6 @@ public partial class WinoExpander : Control
         TemplateSettings.NegativeContentHeight = -1 * (double)e.NewSize.Height;
     }
 
-    private void HeaderTapped(object sender, Microsoft.UI.Xaml.Input.TappedRoutedEventArgs e)
-    {
-        // Tapped is delegated from executing hover action like flag or delete.
-        // No need to toggle the expander.
-
-        if (Header is MailItemDisplayInformationControl itemDisplayInformationControl &&
-            itemDisplayInformationControl.IsRunningHoverAction)
-        {
-            itemDisplayInformationControl.IsRunningHoverAction = false;
-            return;
-        }
-
-        // IsExpanded = !IsExpanded;
-    }
-
     private static void OnIsExpandedChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
     {
         if (obj is WinoExpander control)

Wino.Mail.WinUI/MailAppShell.xaml.cs

@@ -64,28 +64,12 @@ public sealed partial class MailAppShell : MailAppShellAbstract,
             {
                 if (droppedContainer.DataContext is IBaseFolderMenuItem draggingFolder)
                 {
-                    var mailCopies = new List<MailCopy>();
-
                     var dragPackage = e.DataView.Properties[nameof(MailDragPackage)] as MailDragPackage;
 
                     if (dragPackage == null) return;
 
                     e.AcceptedOperation = Windows.ApplicationModel.DataTransfer.DataPackageOperation.Move;
-
-                    // Extract mail copies from IMailItem.
-                    // ThreadViewModels will be divided into pieces.
-
-                    foreach (var item in dragPackage.DraggingMails)
-                    {
-                        if (item is MailItemViewModel singleMailItemViewModel)
-                        {
-                            mailCopies.Add(singleMailItemViewModel.MailCopy);
-                        }
-                        else if (item is ThreadMailItemViewModel threadViewModel)
-                        {
-                            mailCopies.AddRange(threadViewModel.ThreadEmails.Select(a => a.MailCopy));
-                        }
-                    }
+                    var mailCopies = ExtractMailCopies(dragPackage).ToList();
 
                     await ViewModel.PerformMoveOperationAsync(mailCopies, draggingFolder);
                 }
@@ -125,11 +109,36 @@ public sealed partial class MailAppShell : MailAppShellAbstract,
         // Check whether the moving item's account has at least one same as the target folder's account.
         var draggedAccountIds = folderMenuItem.HandlingFolders.Select(a => a.MailAccountId);
 
-        if (!dragPackage.DraggingMails.Cast<MailCopy>().Any(a => draggedAccountIds.Contains(a.AssignedAccount.Id))) return false;
+        var draggedMails = ExtractMailCopies(dragPackage);
+
+        if (!draggedMails.Any()) return false;
+        if (!draggedMails.Any(a => draggedAccountIds.Contains(a.AssignedAccount.Id))) return false;
 
         return true;
     }
 
+    private static IEnumerable<MailCopy> ExtractMailCopies(MailDragPackage dragPackage)
+    {
+        foreach (var item in dragPackage.DraggingMails)
+        {
+            if (item is MailCopy mailCopy)
+            {
+                yield return mailCopy;
+            }
+            else if (item is MailItemViewModel singleMailItemViewModel)
+            {
+                yield return singleMailItemViewModel.MailCopy;
+            }
+            else if (item is ThreadMailItemViewModel threadViewModel)
+            {
+                foreach (var threadMail in threadViewModel.ThreadEmails)
+                {
+                    yield return threadMail.MailCopy;
+                }
+            }
+        }
+    }
+
     private void ItemDragEnterOnFolder(object sender, DragEventArgs e)
     {
         // Validate package content.

Wino.Mail.WinUI/Views/Mail/MailListPage.xaml

@@ -69,10 +69,14 @@
                     <controls:MailItemDisplayInformationControl
                         x:DefaultBindMode="OneWay"
                         ActionItem="{x:Bind}"
+                        CanDrag="True"
                         ContextRequested="MailItemContextRequested"
+                        DragStarting="ThreadHeaderDragStart"
+                        DropCompleted="ThreadHeaderDragFinished"
                         HoverActionExecuted="MailItemDisplayInformationControl_HoverActionExecuted"
                         IsThreadExpanderVisible="True"
-                        MailItemInformation="{x:Bind}" />
+                        MailItemInformation="{x:Bind}"
+                        Tapped="ThreadHeaderTapped" />
                 </controls:WinoExpander.Header>
                 <controls:WinoExpander.Content>
                     <listview:WinoListView
@@ -80,6 +84,7 @@
                         HorizontalContentAlignment="Stretch"
                         toolkitExt:ListViewExtensions.ItemContainerStretchDirection="Horizontal"
                         toolkitExt:ScrollViewerExtensions.VerticalScrollBarMargin="0"
+                        CanDragItems="True"
                         ChoosingItemContainer="WinoListViewChoosingItemContainer"
                         IsItemClickEnabled="True"
                         IsThreadListView="True"
@@ -414,6 +419,24 @@
                         </listview:WinoListView.GroupStyle>
                     </listview:WinoListView>
 
+                    <Border
+                        x:Name="DraggingMessageBorder"
+                        Grid.Row="0"
+                        Margin="14"
+                        Padding="10,6"
+                        HorizontalAlignment="Right"
+                        VerticalAlignment="Bottom"
+                        x:Load="{x:Bind ViewModel.IsDragInProgress, Mode=OneWay}"
+                        Background="{ThemeResource CardBackgroundFillColorDefaultBrush}"
+                        BorderBrush="{ThemeResource CardStrokeColorDefaultBrush}"
+                        BorderThickness="1"
+                        CornerRadius="8">
+                        <TextBlock
+                            FontSize="12"
+                            FontWeight="SemiBold"
+                            Text="{x:Bind ViewModel.DraggingMessageText, Mode=OneWay}" />
+                    </Border>
+
                     <!--  Try online search panel.  -->
                     <Grid Grid.Row="1" Visibility="{x:Bind ViewModel.IsOnlineSearchButtonVisible, Mode=OneWay}">
                         <Button

Wino.Mail.WinUI/Views/Mail/MailListPage.xaml.cs

@@ -63,6 +63,7 @@ public sealed partial class MailListPage : MailListPageAbstract,
         Bindings.Update();
 
         ViewModel.MailCollection.ItemSelectionChanged += WinoMailCollectionSelectionChanged;
+        MailListView.MailDragStateChanged += MailListViewMailDragStateChanged;
 
         UpdateSelectAllButtonStatus();
         UpdateAdaptiveness();
@@ -82,8 +83,10 @@ public sealed partial class MailListPage : MailListPageAbstract,
         this.Bindings.StopTracking();
 
         ViewModel.MailCollection.ItemSelectionChanged -= WinoMailCollectionSelectionChanged;
+        MailListView.MailDragStateChanged -= MailListViewMailDragStateChanged;
         SelectAllCheckbox.Checked -= SelectAllCheckboxChecked;
         SelectAllCheckbox.Unchecked -= SelectAllCheckboxUnchecked;
+        ViewModel.SetDragState(false);
 
         MailListView.Cleanup();
 
@@ -430,29 +433,51 @@ public sealed partial class MailListPage : MailListPageAbstract,
     /// </summary>
     private void ThreadHeaderDragStart(UIElement sender, DragStartingEventArgs args)
     {
-        //if (sender is MailItemDisplayInformationControl control
-        //    && control.ConnectedExpander?.Content is WinoListView contentListView)
-        //{
-        //    var allItems = contentListView.Items.Where(a => a is MailCopy);
+        if (sender is MailItemDisplayInformationControl control && control.ActionItem is ThreadMailItemViewModel threadItem)
+        {
+            args.AllowedOperations = Windows.ApplicationModel.DataTransfer.DataPackageOperation.Move;
 
-        //    // Highlight all items.
-        //    allItems.Cast<MailItemViewModel>().ForEach(a => a.IsCustomFocused = true);
+            // Dragging a thread header should move all mails in that thread.
+            var draggedThreadItems = threadItem.ThreadEmails.Cast<IMailListItem>().ToList();
+            var dragCount = draggedThreadItems.Count;
+            var draggingText = string.Format(Translator.MailsDragging, dragCount);
 
-        //    // Set native drag arg properties.
-        //    args.AllowedOperations = Windows.ApplicationModel.DataTransfer.DataPackageOperation.Move;
+            ViewModel.SetDragState(true, dragCount);
 
-        //    var dragPackage = new MailDragPackage(allItems.Cast<MailCopy>());
+            var dragPackage = new MailDragPackage(draggedThreadItems);
 
-        //    args.Data.Properties.Add(nameof(MailDragPackage), dragPackage);
-        //    args.DragUI.SetContentFromDataPackage();
-
-        //    control.ConnectedExpander.IsExpanded = true;
-        //}
+            args.Data.Properties.Add(nameof(MailDragPackage), dragPackage);
+            args.Data.SetText(draggingText);
+            args.Data.Properties.Title = draggingText;
+            args.DragUI.SetContentFromDataPackage();
+        }
     }
 
     private void ThreadHeaderDragFinished(UIElement sender, DropCompletedEventArgs args)
     {
+        ViewModel.SetDragState(false);
+    }
 
+    private void MailListViewMailDragStateChanged(object? sender, MailDragStateChangedEventArgs e)
+    {
+        ViewModel.SetDragState(e.IsDragging, e.DraggedItemCount);
+    }
+
+    private async void ThreadHeaderTapped(object sender, TappedRoutedEventArgs e)
+    {
+        if (sender is not MailItemDisplayInformationControl control) return;
+
+        // Hover action button clicks bubble a tap as well; skip selecting in that case.
+        if (control.IsRunningHoverAction)
+        {
+            control.IsRunningHoverAction = false;
+            return;
+        }
+
+        if (control.ActionItem is ThreadMailItemViewModel threadItem)
+        {
+            await WinoClickItemInternalAsync(threadItem);
+        }
     }
 
     private async void LeftSwipeItemInvoked(Microsoft.UI.Xaml.Controls.SwipeItem sender, Microsoft.UI.Xaml.Controls.SwipeItemInvokedEventArgs args)
@@ -636,44 +661,74 @@ public sealed partial class MailListPage : MailListPageAbstract,
         // Treat toolbar multi-select mode the same as holding CTRL for click selection behavior.
         bool isCtrlPressed = KeyPressService.IsCtrlKeyPressed() || ViewModel.IsMultiSelectionModeEnabled;
 
-        // Helper local to collapse all other threads (we always collapse ALL then possibly re-expand the active thread per rules)
-        async Task CollapseAllThreadsExceptAsync(ThreadMailItemViewModel? except)
-        {
-            bool wasExpanded = except != null && except.IsThreadExpanded;
+        // Lazily built caches for this invocation.
+        List<ThreadMailItemViewModel>? threadItems = null;
+        Dictionary<string, ThreadMailItemViewModel>? threadById = null;
 
-            await ViewModel.MailCollection.CollapseAllThreadsAsync();
-            if (except != null && wasExpanded)
+        List<ThreadMailItemViewModel> GetThreadItems()
         {
-                // We'll expand explicitly when required by logic below.
-                except.IsThreadExpanded = true;
-            }
-        }
+            if (threadItems != null) return threadItems;
+
+            threadItems = [];
 
-        ThreadMailItemViewModel? FindParentThread(MailItemViewModel mail)
-        {
             foreach (var group in ViewModel.MailCollection.MailItems)
             {
                 foreach (var item in group)
                 {
-                    if (item is ThreadMailItemViewModel thread && thread.ThreadEmails.Contains(mail))
+                    if (item is ThreadMailItemViewModel thread)
                     {
-                        return thread;
+                        threadItems.Add(thread);
                     }
                 }
             }
 
+            return threadItems;
+        }
+
+        ThreadMailItemViewModel? FindParentThread(MailItemViewModel mail)
+        {
+            if (string.IsNullOrEmpty(mail.ThreadId))
+            {
                 return null;
             }
 
+            threadById ??= GetThreadItems()
+                .Where(t => !string.IsNullOrEmpty(t.ThreadId))
+                .GroupBy(t => t.ThreadId, StringComparer.Ordinal)
+                .ToDictionary(g => g.Key, g => g.First(), StringComparer.Ordinal);
+
+            return threadById.TryGetValue(mail.ThreadId, out var threadItem) ? threadItem : null;
+        }
+
+        void CollapseAllThreadsExcept(ThreadMailItemViewModel? except)
+        {
+            foreach (var thread in GetThreadItems())
+            {
+                if (!ReferenceEquals(thread, except) && thread.IsThreadExpanded)
+                {
+                    thread.IsThreadExpanded = false;
+                }
+            }
+        }
+
         static void SyncThreadSelectionFromChildren(ThreadMailItemViewModel? thread)
         {
             if (thread == null) return;
 
-            bool hasSelectedChildren = thread.ThreadEmails.Any(child => child.IsSelected);
+            bool hasSelectedChildren = false;
+            foreach (var child in thread.ThreadEmails)
+            {
+                if (child.IsSelected)
+                {
+                    hasSelectedChildren = true;
+                    break;
+                }
+            }
+
             thread.IsSelected = hasSelectedChildren;
 
             // Keep thread open while it has selected children.
-            if (hasSelectedChildren)
+            if (hasSelectedChildren && !thread.IsThreadExpanded)
             {
                 thread.IsThreadExpanded = true;
             }
@@ -727,7 +782,7 @@ public sealed partial class MailListPage : MailListPageAbstract,
 
             // Reset everything first (exclusive selection scenario)
             await ViewModel.MailCollection.UnselectAllAsync();
-            await CollapseAllThreadsExceptAsync(clickedThread);
+            CollapseAllThreadsExcept(clickedThread);
 
             if (wasThreadSelected && wasThreadExpanded)
             {
@@ -787,20 +842,11 @@ public sealed partial class MailListPage : MailListPageAbstract,
             // If parent thread is already expanded, keep it as-is to avoid collapse/expand animation.
             if (parentThread != null && parentThread.IsThreadExpanded)
             {
-                foreach (var group in ViewModel.MailCollection.MailItems)
-                {
-                    foreach (var item in group)
-                    {
-                        if (item is ThreadMailItemViewModel thread && !ReferenceEquals(thread, parentThread))
-                        {
-                            thread.IsThreadExpanded = false;
-                        }
-                    }
-                }
+                CollapseAllThreadsExcept(parentThread);
             }
             else
             {
-                await ViewModel.MailCollection.CollapseAllThreadsAsync();
+                CollapseAllThreadsExcept(null);
             }
 
             if (parentThread != null && selectExpandThread)