Index: Core/Common/src/Core.Common.Gui/Forms/MainWindow/MainWindow.xaml
===================================================================
diff -u -r8f570abee25de60fe410e7ac7566105b8fa33730 -r28ca59defc5d6928bed9ddcfaf2257467fd8eab2
--- Core/Common/src/Core.Common.Gui/Forms/MainWindow/MainWindow.xaml	(.../MainWindow.xaml)	(revision 8f570abee25de60fe410e7ac7566105b8fa33730)
+++ Core/Common/src/Core.Common.Gui/Forms/MainWindow/MainWindow.xaml	(.../MainWindow.xaml)	(revision 28ca59defc5d6928bed9ddcfaf2257467fd8eab2)
@@ -150,6 +150,7 @@
                     <ToggleButton Name="ButtonShowProjectExplorer" 
                                   Style="{StaticResource ViewStateBarToggleButtonStyle}"
                                   ToolTip="{x:Static properties:Resources.ViewStateBar_ProjectExplorer_ToolTip}"
+                                  Click="ButtonShowProjectExplorer_Click"
                                   AutomationProperties.AutomationId="ViewStateButtonBarShowProjectExplorer">
                         <TextBlock Style="{StaticResource ButtonIconStyle}" Text="&#xE95B;"/>
                     </ToggleButton>
Index: Core/Common/src/Core.Common.Gui/Forms/MainWindow/MainWindow.xaml.cs
===================================================================
diff -u -r8f570abee25de60fe410e7ac7566105b8fa33730 -r28ca59defc5d6928bed9ddcfaf2257467fd8eab2
--- Core/Common/src/Core.Common.Gui/Forms/MainWindow/MainWindow.xaml.cs	(.../MainWindow.xaml.cs)	(revision 8f570abee25de60fe410e7ac7566105b8fa33730)
+++ Core/Common/src/Core.Common.Gui/Forms/MainWindow/MainWindow.xaml.cs	(.../MainWindow.xaml.cs)	(revision 28ca59defc5d6928bed9ddcfaf2257467fd8eab2)
@@ -348,6 +348,22 @@
             ValidateItems();
         }
 
+        private void ButtonShowProjectExplorer_Click(object sender, RoutedEventArgs e)
+        {
+            bool active = viewController.ViewHost.ToolViews.Contains(ProjectExplorer);
+
+            if (active)
+            {
+                viewController.ViewHost.Remove(ProjectExplorer);
+            }
+            else
+            {
+                InitProjectExplorerWindowOrBringToFront();
+            }
+
+            ButtonShowProjectExplorer.IsChecked = !active;
+        }
+
         private void ButtonShowProperties_Click(object sender, RoutedEventArgs e)
         {
             bool active = viewController.ViewHost.ToolViews.Contains(PropertyGrid);