add selected songs count display

src/UI/MainWindow.axaml

@@ -39,7 +39,7 @@
                 </Menu>
 
                 <TabControl>
-                    <TabItem Header="selection">
+                    <TabItem Name="TabSelection" Header="selection">
                         <UserControl Name="SelectionControl"/>
                     </TabItem>
 

src/UI/MainWindow.axaml.cs

@@ -1,8 +1,10 @@
 using System;
+using System.Collections.Specialized;
 using System.Threading.Tasks;
 using Avalonia.Controls;
 using Avalonia.Styling;
 using Avalonia.Threading;
+using MercuryConverter.Data;
 using MercuryConverter.UI.Dialogs;
 using MercuryConverter.UI.Views;
 
@@ -30,6 +32,9 @@ public partial class MainWindow : Window
 
         // Show dialog on startup
         Activated += OnActivated;
+
+        Selection.selections.CollectionChanged += OnDbSelChanged;
+        Database.Songs.CollectionChanged += OnDbSelChanged;
     }
 
     private void OnActivated(object? sender, EventArgs e)
@@ -41,6 +46,14 @@ public partial class MainWindow : Window
         Dialog.IsOpen = true;
     }
 
+    private void OnDbSelChanged(object? sender, NotifyCollectionChangedEventArgs e)
+    {
+        if (Database.Songs.Count > 0)
+        {
+            TabSelection.Header = $"selection ({Selection.selections.Count}/{Database.Songs.Count})";
+        }
+    }
+
     public void OpenDataHandler()
     {
         Dialog.IsOpen = true;

src/UI/Views/Selection/Selection.axaml.cs

@@ -11,7 +11,7 @@ namespace MercuryConverter.UI.Views;
 
 public partial class Selection : Panel
 {
-    private List<Song> selections;
+    public static ObservableRangeCollection<Song> selections = new();
 
     public Selection()
     {
@@ -62,9 +62,19 @@ public partial class Selection : Panel
 
     private void OnSelectionChange(object? sender, SelectionChangedEventArgs e)
     {
-        if (e.AddedItems.Count > 0)
+        selections.Clear();
+        List<Song> sels = new();
+        foreach (Song s in ListingTable.SelectedItems)
         {
-            var song = (Song) e.AddedItems[e.AddedItems.Count-1]!;
+            sels.Add(s);
+        }
+        selections.AddRange(sels);
+
+        if (ListingTable.SelectedItems.Count > 0)
+        {
+            Song song = e.AddedItems.Count > 0 ?
+                (Song) e.AddedItems[e.AddedItems.Count - 1]! :
+                (Song) ListingTable.SelectedItems[ListingTable.SelectedItems.Count - 1]!;
 
             Dispatcher.UIThread.Post(() =>
             {

src/Utils/ObservableRangeCollection.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+
+public class ObservableRangeCollection<T> : ObservableCollection<T>
+{
+    private bool _suppressNotification = false;
+
+    protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
+    {
+        // Only raise the event if notifications are not suppressed
+        if (!_suppressNotification)
+        {
+            base.OnCollectionChanged(e);
+        }
+    }
+
+    public void AddRange(IEnumerable<T> collection)
+    {
+        if (collection == null)
+        {
+            throw new ArgumentNullException(nameof(collection));
+        }
+
+        _suppressNotification = true; // Suppress notifications during bulk add
+
+        foreach (var item in collection)
+        {
+            Items.Add(item); // Add items using the underlying IList<T>
+        }
+
+        _suppressNotification = false; // Re-enable notifications
+
+        // Raise a single Reset event to notify about the bulk change
+        OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+    }
+}