Adding a public API on the View extension that gets triggered when the view extension is closed.

src/DocumentationBrowserViewExtension/DocumentationBrowserViewExtension.cs

@@ -14,7 +14,7 @@ namespace Dynamo.DocumentationBrowser
     /// The DocumentationBrowser view extension displays web or local html files on the Dynamo right panel.
     /// It reacts to documentation display request events in Dynamo to know what and when to display documentation.
     /// </summary>
-    public class DocumentationBrowserViewExtension : IViewExtension, ILogSource
+    public class DocumentationBrowserViewExtension : ViewExtensionBase, IViewExtension, ILogSource
     {
         private ViewLoadedParams viewLoadedParamsReference;
         private MenuItem documentationBrowserMenuItem;
@@ -41,6 +41,7 @@ public DocumentationBrowserViewExtension()
         #region ILogSource
 
         public event Action<ILogMessage> MessageLogged;
+
         internal void OnMessageLogged(ILogMessage msg)
         {
             MessageLogged?.Invoke(msg);
@@ -68,9 +69,6 @@ public void Loaded(ViewLoadedParams viewLoadedParams)
             this.documentationBrowserMenuItem.Unchecked += MenuItemUnCheckedHandler;
             this.viewLoadedParamsReference.AddMenuItem(MenuBarType.View, this.documentationBrowserMenuItem);
 
-
-            DynamoView.CloseExtension += OnCloseExtension;
-
             // subscribe to the documentation open request event from Dynamo
             this.viewLoadedParamsReference.RequestOpenDocumentationLink += HandleRequestOpenDocumentationLink;
 
@@ -96,7 +94,6 @@ public void Shutdown()
         protected virtual void Dispose(bool disposing)
         {
             // Cleanup
-            DynamoView.CloseExtension -= OnCloseExtension;
             this.viewLoadedParamsReference.RequestOpenDocumentationLink -= HandleRequestOpenDocumentationLink;
             this.ViewModel.MessageLogged -= OnViewModelMessageLogged;
             documentationBrowserMenuItem.Checked -= MenuItemCheckHandler;
@@ -138,14 +135,6 @@ public void HandleRequestOpenDocumentationLink(OpenDocumentationLinkEventArgs ar
             this.ViewModel?.HandleOpenDocumentationLinkEvent(args);
         }
 
-        private void OnCloseExtension(String extensionTabName)
-        {
-            if (extensionTabName.Equals(Name))
-            {
-                this.documentationBrowserMenuItem.IsChecked = false;
-            }
-        }
-
         private void OnViewModelMessageLogged(ILogMessage msg)
         {
             OnMessageLogged(msg);
@@ -181,5 +170,10 @@ private void HandleStartPageVisibilityChange(object sender, PropertyChangedEvent
                 ViewModel.ShowBrowser = !dynamoViewModel.ShowStartPage;
             }
         }
+
+        public override void Closed()
+        {
+            this.documentationBrowserMenuItem.IsChecked = false;
+        }
     }
 }

src/DynamoCoreWpf/DynamoCoreWpf.csproj

@@ -96,6 +96,7 @@
     <Compile Include="Controls\UseLevelSpinner.cs" />
     <Compile Include="Extensions\ViewModelCommandExecutive.cs" />
     <Compile Include="Extensions\IViewExtension.cs" />
+    <Compile Include="Extensions\ViewExtensionBase.cs" />
     <Compile Include="Extensions\IViewExtensionLoader.cs" />
     <Compile Include="Extensions\IViewExtensionManager.cs" />
     <Compile Include="Extensions\MenuBarTypeExtensions.cs" />

src/DynamoCoreWpf/Extensions/ViewExtensionBase.cs

@@ -0,0 +1,84 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Dynamo.Wpf.Extensions
+{
+    /// <summary>
+    /// Base class for View Extension.
+    /// </summary>
+    public abstract class ViewExtensionBase : IViewExtension
+    {
+        /// <summary>
+        /// A unique id for this extension instance.  
+        /// 
+        /// There may be multiple instances of the same type, but the application 
+        /// will *not* allow two instances to coexist with the same id.
+        /// </summary>
+        public virtual string UniqueId { get; }
+
+        /// <summary>
+        /// A name for the extension instance.  This is used for more user-readable logging.
+        /// </summary>
+        public virtual string Name { get; }
+
+        /// <summary>
+        /// Dispose method for the view extension.
+        /// </summary>
+        public virtual void Dispose()
+        {
+
+        }
+
+        /// <summary>
+        /// Action to be invoked when DynamoView begins to start up.  This is guaranteed to happen
+        /// after the DynamoModel has been created.
+        /// 
+        /// This method is *not* guaranteed to be invoked unless the extension is present
+        /// at startup.
+        /// 
+        /// Exceptions thrown from this method will be caught by Dynamo and 
+        /// displayed.
+        /// </summary>
+        public virtual void Loaded(ViewLoadedParams viewLoadedParams)
+        {
+
+        }
+
+        /// <summary>
+        /// Action to be invoked when shutdown has begun.  This gives the UI a last minute chance to interact
+        /// with the user.
+        /// 
+        /// This action is guaranteed to be invoked before the associated model layer method on IExtension.
+        /// </summary>
+        public virtual void Shutdown()
+        {
+
+        }
+
+        /// <summary>
+        /// Action to be invoked when DynamoView begins to start up.  This is guaranteed to happen
+        /// after the DynamoModel has been created.
+        /// 
+        /// This method is *not* guaranteed to be invoked unless the extension is present
+        /// at startup.
+        /// 
+        /// Exceptions thrown from this method will be caught by Dynamo and 
+        /// displayed.
+        /// </summary>
+        public virtual void Startup(ViewStartupParams viewStartupParams)
+        {
+
+        }
+
+        /// <summary>
+        /// Action to be invoked when the view extenion is closed. 
+        /// </summary>
+        public virtual void Closed()
+        {
+
+        }
+    }
+}

src/DynamoCoreWpf/Views/Core/DynamoView.xaml.cs

@@ -288,7 +288,9 @@ internal void CloseExtensionControl(IViewExtension viewExtension)
         {
             string tabName = viewExtension.Name;
             TabItem tabitem = ExtensionTabItems.OfType<TabItem>().SingleOrDefault(n => n.Header.ToString() == tabName);
-            CloseExtension?.Invoke(tabName);
+
+            var viewExtensionBaseClass = (ViewExtensionBase) viewExtension;
+            viewExtensionBaseClass.Closed();
             CloseExtensionTab(tabitem);
             CloseExtensionWindow(tabName);
         }
@@ -302,10 +304,10 @@ internal void CloseExtensionControl(IViewExtension viewExtension)
         internal void CloseExtensionTab(object sender, RoutedEventArgs e)
         {
             string tabName = (sender as Button).DataContext.ToString();
-
-            CloseExtension?.Invoke(tabName);
-
             TabItem tabitem = ExtensionTabItems.OfType<TabItem>().SingleOrDefault(n => n.Header.ToString() == tabName);
+
+            var viewExtensionBaseClass = (ViewExtensionBase) tabitem.Tag;
+            viewExtensionBaseClass.Closed();
             CloseExtensionTab(tabitem);
         }
 
@@ -320,7 +322,7 @@ private void CloseExtensionTab(TabItem tabitem)
             // get the selected tab
             TabItem selectedTab = tabDynamic.SelectedItem as TabItem;
 
-            if (tabToBeRemoved != null)
+            if (tabToBeRemoved != null && ExtensionTabItems.Count > 0)
             {
                 // clear tab control binding and bind to the new tab-list. 
                 tabDynamic.DataContext = null;
@@ -416,7 +418,8 @@ private void ExtensionWindow_Closed(object sender, EventArgs e)
             }
             else
             {
-                CloseExtension?.Invoke(extName);
+                var viewExtensionBaseClass = (ViewExtensionBase)ext.Tag;
+                viewExtensionBaseClass.Closed();
             }
         }
 

src/WorkspaceDependencyViewExtension/WorkspaceDependencyView.xaml.cs

@@ -177,7 +177,6 @@ public WorkspaceDependencyView(WorkspaceDependencyViewExtension viewExtension, V
             packageInstaller = p.PackageInstaller;
             dependencyViewExtension = viewExtension;
             DependencyRegen(currentWorkspace);
-            DynamoView.CloseExtension += this.OnExtensionTabClosedHandler;
             HomeWorkspaceModel.WorkspaceClosed += this.CloseExtensionTab;
         }
 
@@ -189,20 +188,6 @@ internal void CloseExtensionTab()
             loadedParams.CloseExtensioninInSideBar(dependencyViewExtension);
         }
 
-        /// <summary>
-        /// This event is raised when an extension tab is closed and this event 
-        /// is subscribed by the Workspace dependency view extension.
-        /// <param name="extensionTabName"></param>
-        /// </summary>
-        internal event Action<String> OnExtensionTabClosed;
-        private void OnExtensionTabClosedHandler(String extensionTabName)
-        {
-            if (OnExtensionTabClosed != null)
-            {
-                OnExtensionTabClosed(extensionTabName);
-            }
-        }
-
         /// <summary>
         /// Send a request to the package manager client to download this package and its dependencies
         /// </summary>
@@ -282,7 +267,6 @@ public void Dispose()
             loadedParams.CurrentWorkspaceCleared -= OnWorkspaceCleared;
             currentWorkspace.PropertyChanged -= OnWorkspacePropertyChanged;
             WorkspaceModel.DummyNodesReloaded -= TriggerDependencyRegen;
-            DynamoView.CloseExtension -= this.OnExtensionTabClosedHandler;
             HomeWorkspaceModel.WorkspaceClosed -= this.CloseExtensionTab;
             PackageDependencyTable.ItemsSource = null;
             dataRows = null;

src/WorkspaceDependencyViewExtension/WorkspaceDependencyViewExtension.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Linq;
 using System.Windows.Controls;
+using Dynamo.Controls;
 using Dynamo.Extensions;
 using Dynamo.Graph.Workspaces;
 using Dynamo.Logging;
@@ -15,7 +16,7 @@ namespace Dynamo.WorkspaceDependency
     /// which tracks graph dependencies (currently only packages) on the Dynamo right panel.
     /// It reacts to workspace modified/ cleared events to refresh.
     /// </summary>
-    public class WorkspaceDependencyViewExtension : IViewExtension, ILogSource
+    public class WorkspaceDependencyViewExtension : ViewExtensionBase, IViewExtension, ILogSource
     {
         internal MenuItem workspaceReferencesMenuItem;
         private readonly String extensionName = Properties.Resources.ExtensionName;
@@ -55,7 +56,6 @@ public string UniqueId
         /// </summary>
         public void Dispose()
         {
-            DependencyView.OnExtensionTabClosed -= OnCloseExtension;
             DependencyView.Dispose();
         }
 
@@ -82,14 +82,6 @@ internal void OnMessageLogged(ILogMessage msg)
             this.MessageLogged?.Invoke(msg);
         }
 
-        internal void OnCloseExtension(String extensionTabName)
-        {
-            if (extensionTabName.Equals(extensionName))
-            {
-                this.workspaceReferencesMenuItem.IsChecked = false;
-            }  
-        }
-
         public void Loaded(ViewLoadedParams viewLoadedParams)
         {
             DependencyView = new WorkspaceDependencyView(this, viewLoadedParams);
@@ -101,8 +93,6 @@ public void Loaded(ViewLoadedParams viewLoadedParams)
                 DependencyView.DependencyRegen(viewLoadedParams.CurrentWorkspaceModel as WorkspaceModel);
             };
 
-            DependencyView.OnExtensionTabClosed += OnCloseExtension;
-
             // Adding a button in view menu to refresh and show manually
             workspaceReferencesMenuItem = new MenuItem { Header = Resources.MenuItemString, IsCheckable = true, IsChecked = false };
             workspaceReferencesMenuItem.Click += (sender, args) =>
@@ -119,10 +109,13 @@ public void Loaded(ViewLoadedParams viewLoadedParams)
                     viewLoadedParams.CloseExtensioninInSideBar(this);
                     workspaceReferencesMenuItem.IsChecked = false;
                 }
-
             };
             viewLoadedParams.AddMenuItem(MenuBarType.View, workspaceReferencesMenuItem);
         }
 
+        public override void Closed()
+        {
+            this.workspaceReferencesMenuItem.IsChecked = false;
+        }
     }
 }

test/DynamoCoreWpfTests/ViewExtensions/WorkspaceDependencyViewExtensionTests.cs

@@ -129,6 +129,35 @@ public void APItoCloseViewExtensionTabTest()
             Assert.AreEqual(0, View.ExtensionTabItems.Count);
         }
 
+        /// <summary>
+        /// This test will verify that the Closed() will be triggered on the extension that is closed. 
+        /// </summary>
+        [Test]
+        public void OnViewExtensionClosedTest()
+        {
+            RaiseLoadedEvent(this.View);
+            var extensionManager = View.viewExtensionManager;
+            WorkspaceDependencyViewExtension workspaceDependencyViewExtension = (WorkspaceDependencyViewExtension) extensionManager.ViewExtensions
+                                                                                .Where(ve => ve.Name.Equals("Workspace References")).FirstOrDefault();
+            // Open a graph which should bring up the Workspace References view extension window with one tab
+            Open(@"pkgs\Dynamo Samples\extra\CustomRenderExample.dyn");
+            Assert.AreEqual(1, View.ExtensionTabItems.Count);
+
+            var loadedParams = new ViewLoadedParams(View, ViewModel);
+
+            // Assert that the workspace references menu item is checked.
+            Assert.IsTrue(workspaceDependencyViewExtension.workspaceReferencesMenuItem.IsChecked);
+
+            // Closing the view extension side bar should trigger the Closed() on the workspace dependency view extension.
+            // This will un-check the workspace references menu item.
+            loadedParams.CloseExtensioninInSideBar(workspaceDependencyViewExtension);
+
+            Assert.AreEqual(0, View.ExtensionTabItems.Count);
+
+            // Assert that the workspace references menu item is un-checked.
+            Assert.IsFalse(workspaceDependencyViewExtension.workspaceReferencesMenuItem.IsChecked);
+        }
+
         /// <summary>
         /// This test will make sure that the extension tab is closed upon closing the home workspace.
         /// </summary>