Index: Core/Common/src/Core.Common.Gui/Forms/MainWindow/MainWindow.xaml.cs
===================================================================
diff -u -r28ca59defc5d6928bed9ddcfaf2257467fd8eab2 -rc063a97260cc4d630a453c359d49fca96ed8ac80
--- Core/Common/src/Core.Common.Gui/Forms/MainWindow/MainWindow.xaml.cs	(.../MainWindow.xaml.cs)	(revision 28ca59defc5d6928bed9ddcfaf2257467fd8eab2)
+++ Core/Common/src/Core.Common.Gui/Forms/MainWindow/MainWindow.xaml.cs	(.../MainWindow.xaml.cs)	(revision c063a97260cc4d630a453c359d49fca96ed8ac80)
@@ -223,6 +223,17 @@
             }
         }
 
+        /// <summary>
+        /// Updates the data of the <see cref="ProjectExplorer"/>.
+        /// </summary>
+        public void UpdateProjectExplorer()
+        {
+            if (ProjectExplorer != null)
+            {
+                ProjectExplorer.Data = gui.Project;
+            }
+        }
+
         protected virtual void Dispose(bool disposing)
         {
             if (IsWindowDisposed || !disposing)
Index: Core/Common/src/Core.Common.Gui/GuiCore.cs
===================================================================
diff -u -r229c2919ec8ea593f593b614ca64d4c42a5b8534 -rc063a97260cc4d630a453c359d49fca96ed8ac80
--- Core/Common/src/Core.Common.Gui/GuiCore.cs	(.../GuiCore.cs)	(revision 229c2919ec8ea593f593b614ca64d4c42a5b8534)
+++ Core/Common/src/Core.Common.Gui/GuiCore.cs	(.../GuiCore.cs)	(revision c063a97260cc4d630a453c359d49fca96ed8ac80)
@@ -368,6 +368,7 @@
 
             projectObserver.Observable = newProject;
             UpdateTitle();
+            mainWindow?.UpdateProjectExplorer();
         }
 
         private void ApplicationBeforeProjectOpened(IProject oldProject)
Index: Core/Common/test/Core.Common.Gui.Test/Forms/MainWindow/MainWindowTest.cs
===================================================================
diff -u -r667f6bc7aad5f7fc5b82da1b0577d92d392e91a4 -rc063a97260cc4d630a453c359d49fca96ed8ac80
--- Core/Common/test/Core.Common.Gui.Test/Forms/MainWindow/MainWindowTest.cs	(.../MainWindowTest.cs)	(revision 667f6bc7aad5f7fc5b82da1b0577d92d392e91a4)
+++ Core/Common/test/Core.Common.Gui.Test/Forms/MainWindow/MainWindowTest.cs	(.../MainWindowTest.cs)	(revision c063a97260cc4d630a453c359d49fca96ed8ac80)
@@ -584,5 +584,61 @@
 
             mocks.VerifyAll();
         }
+
+        [Test]
+        [Apartment(ApartmentState.STA)]
+        public void GivenGuiWithProjectExplorer_WhenUpdateProjectExplorer_ThenDataSetOnProjectExplorer()
+        {
+            // Given
+            var mocks = new MockRepository();
+            var project1 = mocks.Stub<IProject>();
+            var project2 = mocks.Stub<IProject>();
+
+            var projectStore = mocks.Stub<IStoreProject>();
+            var projectMigrator = mocks.Stub<IMigrateProject>();
+            var projectFactory = mocks.Stub<IProjectFactory>();
+            projectFactory.Stub(pf => pf.CreateNewProject()).Return(project1);
+            
+            var plugin = mocks.Stub<PluginBase>();
+            plugin.Stub(p => p.Deactivate());
+            plugin.Stub(p => p.Dispose());
+            plugin.Expect(p => p.Activate());
+            plugin.Expect(p => p.GetViewInfos()).Return(Enumerable.Empty<ViewInfo>());
+            plugin.Expect(p => p.GetPropertyInfos()).Return(Enumerable.Empty<PropertyInfo>());
+            plugin.Expect(p => p.GetChildDataWithViewDefinitions(null)).IgnoreArguments().Return(Enumerable.Empty<object>());
+            plugin.Stub(p => p.GetTreeNodeInfos()).Return(new TreeNodeInfo[]
+            {
+                new TreeNodeInfo<IProject>()
+            });
+            mocks.ReplayAll();
+            
+            using (var mainWindow = new Gui.Forms.MainWindow.MainWindow())
+            using (var gui = new GuiCore(mainWindow, projectStore, projectMigrator, projectFactory, new GuiCoreSettings())
+            {
+                Plugins =
+                {
+                    plugin
+                }
+            })
+            {
+                gui.Run();
+                
+                mainWindow.SetGui(gui);
+                mainWindow.InitializeToolWindows();
+
+                // Precondition
+                Assert.IsNotNull(mainWindow.ProjectExplorer);
+                Assert.AreSame(project1, mainWindow.ProjectExplorer.Data);
+                
+                gui.SetProject(project2, string.Empty);
+
+                // When
+                mainWindow.UpdateProjectExplorer();
+                
+                // Then
+                Assert.AreSame(project2, mainWindow.ProjectExplorer.Data);
+            }
+            mocks.VerifyAll();
+        }
     }
 }
\ No newline at end of file
Index: Core/Common/test/Core.Common.Gui.Test/GuiCoreTest.cs
===================================================================
diff -u -r667f6bc7aad5f7fc5b82da1b0577d92d392e91a4 -rc063a97260cc4d630a453c359d49fca96ed8ac80
--- Core/Common/test/Core.Common.Gui.Test/GuiCoreTest.cs	(.../GuiCoreTest.cs)	(revision 667f6bc7aad5f7fc5b82da1b0577d92d392e91a4)
+++ Core/Common/test/Core.Common.Gui.Test/GuiCoreTest.cs	(.../GuiCoreTest.cs)	(revision c063a97260cc4d630a453c359d49fca96ed8ac80)
@@ -632,6 +632,7 @@
 
                 var expectedTitle = $"{fileName} - {fixedSettings.MainWindowTitle} {SettingsHelper.Instance.ApplicationVersion}";
                 Assert.AreEqual(expectedTitle, mainWindow.Title);
+                Assert.AreSame(gui.Project, mainWindow.ProjectExplorer.Data);
             }
 
             mocks.VerifyAll();