New .Net 4.5 Feature

No longer using the Dispatcher thread to access ObservableCollection from Non-UI Background Thread:

https://docs.microsoft.com/en-us/dotnet/framework/wpf/getting-started/whats-new#xthread_access

source/Components/FilterTreeViewLib/ViewModels/Tree/MetaLocationRootViewModel.cs

@@ -8,22 +8,21 @@
     using System.Linq;
     using System.Threading;
     using System.Threading.Tasks;
-    using System.Windows;
+    using System.Windows.Data;
     using System.Windows.Input;
-    using System.Windows.Threading;
 
     /// <summary>
     /// Implements the root viewmodel of the tree structure to be presented in a treeview.
     /// </summary>
     public class MetaLocationRootViewModel : Base.BaseViewModel
     {
         #region fields
-        private const DispatcherPriority _ChildrenEditPrio = DispatcherPriority.DataBind;
-
         protected readonly ObservableCollection<MetaLocationViewModel> _CountryRootItems = null;
         protected readonly IList<MetaLocationViewModel> _BackUpCountryRoots = null;
 
         private ICommand _ExpandCommand;
+
+        private object _itemsLock = new object();
         #endregion fields
 
         #region constructors
@@ -33,6 +32,8 @@ public class MetaLocationRootViewModel : Base.BaseViewModel
         public MetaLocationRootViewModel()
         {
             _CountryRootItems = new ObservableCollection<MetaLocationViewModel>();
+            BindingOperations.EnableCollectionSynchronization(_CountryRootItems, _itemsLock);
+
             _BackUpCountryRoots = new List<MetaLocationViewModel>(400);
         }
         #endregion constructors
@@ -109,14 +110,13 @@ string zipContainerFile
 
             foreach (var item in isoCountries)
             {
-                Application.Current.Dispatcher.Invoke(() =>
+                lock (_itemsLock)
                 {
                     var vmItem = MetaLocationViewModel.GetViewModelFromModel(item);
 
                     RootsAdd(vmItem, true);
                     //Root.RootsAdd(vmItem, false); // Make all items initially visible
-
-                }, DispatcherPriority.ApplicationIdle);
+                }
             }
         }
 
@@ -155,7 +155,10 @@ public int DoSearch(SearchParams searchParams, CancellationToken token)
             searchParams.SearchStringTrim();
             searchParams.SearchStringToUpperCase();
 
-            Application.Current.Dispatcher.Invoke(() => { root.Clear(); }, _ChildrenEditPrio);
+            lock (_itemsLock)
+            {
+                root.Clear();
+            }
 
             // Show all root items if string to search is empty
             if (searchParams.IsSearchStringEmpty == true ||
@@ -170,7 +173,10 @@ public int DoSearch(SearchParams searchParams, CancellationToken token)
                     rootItem.ChildrenClear(false);
                     rootItem.SetExpand(false);
 
-                    Application.Current.Dispatcher.Invoke(() => { root.Add(rootItem); }, _ChildrenEditPrio);
+                    lock (_itemsLock)
+                    {
+                        root.Add(rootItem);
+                    }
                 }
 
                 return 0;
@@ -217,7 +223,11 @@ public int DoSearch(SearchParams searchParams, CancellationToken token)
                         rootItem.SetExpand(false);
 
                     //Console.WriteLine("node: {0} match count: {1}", rootItem.LocalName, nodeMatchCount);
-                    Application.Current.Dispatcher.Invoke(() => { root.Add(rootItem); }, _ChildrenEditPrio);
+                    lock (_itemsLock)
+                    {
+                        root.Add(rootItem);
+                    }
+
                 }
             }
 

source/Components/FilterTreeViewLib/ViewModels/Tree/MetaLocationViewModel.cs

@@ -8,17 +8,14 @@
     using System.Collections.Generic;
     using System.Collections.ObjectModel;
     using System.Linq;
-    using System.Windows;
-    using System.Windows.Threading;
+    using System.Windows.Data;
 
     /// <summary>
     /// Implements an items viewmodel that should be bound to an items collection in a tree view.
     /// </summary>
     public class MetaLocationViewModel : Base.BaseViewModel, IHasDummyChild
     {
         #region fields
-        private static DispatcherPriority _ChildrenEditPrio = DispatcherPriority.Normal;
-
         private static readonly MetaLocationViewModel DummyChild = new MetaLocationViewModel();
 
         private bool _IsItemExpanded;
@@ -28,6 +25,8 @@ public class MetaLocationViewModel : Base.BaseViewModel, IHasDummyChild
         private MatchType _Match;
         private string _LocalName;
         private ISelectionRange _Range = null;
+
+        private object _itemsLock = new object();
         #endregion fields
 
         #region constructors
@@ -56,10 +55,11 @@ BusinessLib.Models.MetaLocationModel locationModel
         /// </summary>
         protected MetaLocationViewModel()
         {
-            ////            _IsItemVisible = true;
             _IsItemExpanded = false;
 
             _Children = new ObservableCollection<MetaLocationViewModel>();
+            BindingOperations.EnableCollectionSynchronization(_Children, _itemsLock);
+
             _BackUpNodes = new List<MetaLocationViewModel>();
 
             _Match = MatchType.NoMatch;
@@ -377,15 +377,14 @@ internal void ChildrenClear(bool bClearBackup = true
         {
             try
             {
-                Application.Current.Dispatcher.Invoke(() =>
+                lock (_itemsLock)
                 {
                     _Children.Clear();
 
                     // Cities do not have children so we need no dummy child here
                     if (bAddDummyChild == true && TypeOfLocation != LocationType.City)
                         _Children.Add(DummyChild);
-
-                }, _ChildrenEditPrio);
+                }
 
                 if (bClearBackup == true)
                     _BackUpNodes.Clear();
@@ -487,10 +486,16 @@ private void ChildrenAdd(MetaLocationViewModel child, bool bAddBackup = true)
             {
                 if (HasDummyChild == true)
                 {
-                    Application.Current.Dispatcher.Invoke(() => { _Children.Clear(); }, _ChildrenEditPrio);
+                    lock (_itemsLock)
+                    {
+                        _Children.Clear();
+                    }
                 }
 
-                Application.Current.Dispatcher.Invoke(() => { _Children.Add(child); }, _ChildrenEditPrio);
+                lock (_itemsLock)
+                {
+                    _Children.Add(child);
+                }
 
                 if (bAddBackup == true)
                     _BackUpNodes.Add(child);
@@ -511,11 +516,14 @@ private void ChildrenAddBackupNodes(MetaLocationViewModel child)
 
         private void ChildrenRemove(MetaLocationViewModel child, bool bRemoveBackup = true)
         {
-            Application.Current.Dispatcher.Invoke(() => { _Children.Remove(child); }, _ChildrenEditPrio);
+            lock (_itemsLock)
+            {
+                _Children.Remove(child);
+            }
 
             if (bRemoveBackup == true)
                 _BackUpNodes.Remove(child);
         }
-#endregion methods
+        #endregion methods
     }
 }