From d65e9a9019867b1019810329727c154cc20b4c90 Mon Sep 17 00:00:00 2001
From: Dirkster99 <Dirk.Bahle@gmx.de>
Date: Thu, 14 Feb 2019 19:45:52 +0100
Subject: [PATCH] LayoutRoot doesn't notify change for Children or
 ChildrenCount #1313 https://github.com/xceedsoftware/wpftoolkit/issues/1313

---
 .../Xceed.Wpf.AvalonDock/Layout/LayoutRoot.cs | 79 ++++++++++++++++---
 1 file changed, 66 insertions(+), 13 deletions(-)

diff --git a/source/Components/Xceed.Wpf.AvalonDock/Layout/LayoutRoot.cs b/source/Components/Xceed.Wpf.AvalonDock/Layout/LayoutRoot.cs
index 78b39e25..e5da640a 100644
--- a/source/Components/Xceed.Wpf.AvalonDock/Layout/LayoutRoot.cs
+++ b/source/Components/Xceed.Wpf.AvalonDock/Layout/LayoutRoot.cs
@@ -771,32 +771,63 @@ internal void OnLayoutElementRemoved( LayoutElement element )
         ElementRemoved( this, new LayoutElementEventArgs( element ) );
     }
 
-    #endregion
+        #endregion
 
     #region Private Methods
 
-    private void _floatingWindows_CollectionChanged( object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e )
+    private void _floatingWindows_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
     {
-      if( e.OldItems != null && ( e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove ||
-          e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Replace ) )
+      bool bNotifyChildren = false;
+
+      if (e.OldItems != null && (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove ||
+          e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Replace))
       {
-        foreach( LayoutFloatingWindow element in e.OldItems )
+        foreach (LayoutFloatingWindow element in e.OldItems)
         {
-          if( element.Parent == this )
+          if (element.Parent == this)
+          {
             element.Parent = null;
+            bNotifyChildren = true;
+          }
         }
       }
 
-      if( e.NewItems != null && ( e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add ||
-          e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Replace ) )
+      if (e.NewItems != null && (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add ||
+          e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Replace))
       {
-        foreach( LayoutFloatingWindow element in e.NewItems )
+        foreach (LayoutFloatingWindow element in e.NewItems)
+        {
           element.Parent = this;
+          bNotifyChildren = true;
+        }
       }
-    }
 
+      // descendants of LayoutElement notify when their Children and ChildrenCount properties change
+      // https://github.com/xceedsoftware/wpftoolkit/issues/1313
+      //
+      if (bNotifyChildren == true &&
+          (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove ||
+              e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add
+          ))
+      {
+        RaisePropertyChanged("Children");
+        RaisePropertyChanged("ChildrenCount");
+      }
+      else
+      {
+        if (bNotifyChildren == true &&
+            e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Replace)
+        {
+          RaisePropertyChanged("Children");
+        }
+      }
+    }
+    
+    
     private void _hiddenAnchorables_CollectionChanged( object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e )
     {
+      bool bNotifyChildren = false;
+
       if( e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove ||
           e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Replace )
       {
@@ -804,8 +835,11 @@ private void _hiddenAnchorables_CollectionChanged( object sender, System.Collect
         {
           foreach( LayoutAnchorable element in e.OldItems )
           {
-            if( element.Parent == this )
+            if( element.Parent == this)
+            {
               element.Parent = null;
+              bNotifyChildren = true;
+            }
           }
         }
       }
@@ -821,15 +855,34 @@ private void _hiddenAnchorables_CollectionChanged( object sender, System.Collect
             {
               if( element.Parent != null )
                 element.Parent.RemoveChild( element );
+
               element.Parent = this;
+              bNotifyChildren = true;
             }
 
           }
         }
       }
 
-
-
+      // descendants of LayoutElement notify when their Children and ChildrenCount properties change
+      // https://github.com/xceedsoftware/wpftoolkit/issues/1313
+      //
+      if (bNotifyChildren == true &&
+          (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove ||
+           e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add
+         ))
+      {
+          RaisePropertyChanged("Children");
+          RaisePropertyChanged("ChildrenCount");
+      }
+      else
+      {
+        if (bNotifyChildren == true &&
+            e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Replace )
+        {
+          RaisePropertyChanged("Children");
+        }
+      }
     }
 
     private void InternalSetActiveContent( LayoutContent currentValue, LayoutContent newActiveContent )