init

Common/DTS.CommonCore/Behaviors/MultiSelectionBehavior.cs

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+using DTS.Common.Enums;
+using DTS.Common.Utilities.Logging;
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.Linq;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Interactivity;
+namespace DTS.Common.Behaviors
+{
+    public class MultiSelectionBehavior : Behavior<ListBox>
+    {
+        protected override void OnAttached()
+        {
+            base.OnAttached();
+            if (SelectedItems != null)
+            {
+                AssociatedObject.SelectedItems.Clear();
+                foreach (var item in SelectedItems)
+                {
+                    AssociatedObject.SelectedItems.Add(item);
+                }
+            }
+        }
+
+        public IList SelectedItems
+        {
+            get => (IList)GetValue(SelectedItemsProperty);
+            set => SetValue(SelectedItemsProperty, value);
+        }
+
+        public static readonly DependencyProperty SelectedItemsProperty =
+            DependencyProperty.Register("SelectedItems", typeof(IList), typeof(MultiSelectionBehavior), new UIPropertyMetadata(null, SelectedItemsChanged));
+
+        private static void SelectedItemsChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
+        {
+            var behavior = o as MultiSelectionBehavior;
+            if (behavior == null)
+                return;
+
+
+            if (e.OldValue is INotifyCollectionChanged oldValue)
+            {
+                oldValue.CollectionChanged -= behavior.SourceCollectionChanged;
+                behavior.AssociatedObject.SelectionChanged -= behavior.ListBoxSelectionChanged;
+            }
+            if (e.NewValue is INotifyCollectionChanged newValue)
+            {
+                behavior.AssociatedObject.SelectedItems.Clear();
+                foreach (var item in (IEnumerable)newValue)
+                {
+                    behavior.AssociatedObject.SelectedItems.Add(item);
+                }
+
+                behavior.AssociatedObject.SelectionChanged += behavior.ListBoxSelectionChanged;
+                newValue.CollectionChanged += behavior.SourceCollectionChanged;
+            }
+        }
+
+        private bool _isUpdatingTarget;
+        private bool _isUpdatingSource;
+
+        private void SourceCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+        {
+            if (_isUpdatingSource)
+                return;
+
+            try
+            {
+                _isUpdatingTarget = true;
+
+                if (e.OldItems != null)
+                {
+                    foreach (var item in e.OldItems)
+                    {
+                        AssociatedObject.SelectedItems.Remove(item);
+                    }
+                }
+
+                if (e.NewItems != null)
+                {
+                    foreach (var item in e.NewItems)
+                    {
+                        AssociatedObject.SelectedItems.Add(item);
+                    }
+                }
+                
+                if (e.Action == NotifyCollectionChangedAction.Reset)
+                {
+                    AssociatedObject.SelectedItems.Clear();
+                }
+            }
+            finally
+            {
+                _isUpdatingTarget = false;
+            }
+        }
+
+        private void ListBoxSelectionChanged(object sender, SelectionChangedEventArgs e)
+        {
+            if (_isUpdatingTarget)
+                return;
+            
+            var selectedItems = SelectedItems;
+            if (selectedItems == null)
+                return;
+            //this could be a bulk operation, turn off notifications if consumer is paying attention
+            SelectedItemsStatus.SetUpdating(SelectedItems, true);
+            try
+            {
+                _isUpdatingSource = true;
+                foreach (var item in e.RemovedItems)
+                {
+                    selectedItems.Remove(item);
+                }
+
+                var itemsToAdd = new List<object>();
+
+                foreach (var item in e.AddedItems)
+                {
+                    if (!selectedItems.Contains(item))
+                    {
+                        itemsToAdd.Add(item);
+                    }
+                }
+
+                var type = selectedItems.GetType().GenericTypeArguments[0];
+
+                foreach (var item in itemsToAdd)
+                {
+                    if (item == itemsToAdd.Last())
+                    {
+                        //if this is the last item, turn notifications back on
+                        SelectedItemsStatus.SetUpdating(SelectedItems, false);
+                    }
+
+                    try
+                    {
+                        if (type.IsAssignableFrom(item.GetType()))
+                        {
+                            selectedItems.Add(item);
+                        }
+                    }
+                    catch (Exception ex)
+                    {
+                        APILogger.Log(ex);
+                    }
+                }
+            }
+            finally
+            {
+                _isUpdatingSource = false;          
+            }
+
+        }
+
+    }
+}