loads both toolwindows; access violation crash on exit (Rubberduck crash repro!)

Author: retailcoder

App.cs

@@ -1,29 +1,35 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using Microsoft.Vbe.Interop;
+using Microsoft.Vbe.Interop;
 
 namespace SlimDucky
 {
     public class App
     {
         private readonly VBE _vbe;
+        private readonly AddIn _adddIn;
 
-        public App(VBE vbe)
+        public App(VBE vbe, AddIn addIn)
         {
             _vbe = vbe;
+            _adddIn = addIn;
+
+            _winFormsUserControl = new WinFormsControl();
+            _wpfUserControl = new WpfHostControl();
         }
 
+        private IDockableUserControl _wpfUserControl;
+        private IDockableUserControl _winFormsUserControl;
+
         public void Startup()
         {
-            
+            var winFormsPresenter = new DockableToolwindowPresenter(_vbe, _adddIn, _winFormsUserControl);
+            var wpfPresenter = new DockableToolwindowPresenter(_vbe, _adddIn, _wpfUserControl);
+
+            winFormsPresenter.Show();
+            wpfPresenter.Show();
         }
 
         public void Shutdown()
         {
-            
         }
     }
 }

Connect.cs

@@ -85,7 +85,7 @@ private void InitializeAddIn()
                 return;
             }
 
-            _app = new App(_vbe);
+            _app = new App(_vbe, _addIn);
             _app.Startup();
 
             _isInitialized = true;

DockableToolwindowPresenter.cs

@@ -0,0 +1,83 @@
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Windows.Forms;
+using Microsoft.Vbe.Interop;
+
+namespace SlimDucky
+{
+    public class DockableToolwindowPresenter
+    {
+        private readonly AddIn _addin;
+        private readonly Window _window;
+        private readonly VBE _vbe;
+
+        private object _userControlObject;
+
+        public DockableToolwindowPresenter(VBE vbe, AddIn addin, IDockableUserControl view)
+        {
+            _vbe = vbe;
+            _addin = addin;
+            UserControl = view;
+            _window = CreateToolWindow(view);
+        }
+
+        public IDockableUserControl UserControl { get; }
+
+        private Window CreateToolWindow(IDockableUserControl view)
+        {
+            Window toolWindow;
+            try
+            {
+                object control = null;
+                toolWindow = _vbe.Windows.CreateToolWindow(_addin, _DockableWindowHost.ProgId, view.Caption, view.ClassId, ref control);
+                _userControlObject = control;
+            }
+            catch(COMException exception)
+            {
+                Debug.WriteLine(exception);
+                throw;
+            }
+
+            var userControlHost = (_DockableWindowHost)_userControlObject;
+            toolWindow.Visible = true; //window resizing doesn't work without this
+
+            EnsureMinimumWindowSize(toolWindow);
+
+            toolWindow.Visible = true; // here Rubberduck checks window settings to show toolwindow at startup
+
+            userControlHost.AddUserControl(view as UserControl, new IntPtr(_vbe.MainWindow.HWnd));
+            return toolWindow;
+        }
+
+        private void EnsureMinimumWindowSize(Window window)
+        {
+            const int defaultWidth = 350;
+            const int defaultHeight = 200;
+
+            if(!window.Visible || window.LinkedWindows != null)
+            {
+                return;
+            }
+
+            if(window.Width < defaultWidth)
+            {
+                window.Width = defaultWidth;
+            }
+
+            if(window.Height < defaultHeight)
+            {
+                window.Height = defaultHeight;
+            }
+        }
+
+        public virtual void Show() => _window.Visible = true;
+        public virtual void Hide() => _window.Visible = false;
+
+        ~DockableToolwindowPresenter()
+        {
+            // destructor for tracking purposes only - do not suppress unless 
+            Debug.WriteLine("DockableToolwindowPresenter finalized.");
+        }
+    }
+}

IDockableUserControl.cs

@@ -0,0 +1,15 @@
+namespace SlimDucky
+{
+    public interface IDockableUserControl
+    {
+        /// <summary>
+        /// Gets a string containing the GUID with which the class is registered.
+        /// </summary>
+        string ClassId { get; }
+
+        /// <summary>
+        /// Gets a string containing the caption of the toolwindow.
+        /// </summary>
+        string Caption { get; }
+    }
+}

Properties/AssemblyInfo.cs

@@ -17,7 +17,7 @@
 // Setting ComVisible to false makes the types in this assembly not visible 
 // to COM components.  If you need to access a type in this assembly from 
 // COM, set the ComVisible attribute to true on that type.
-[assembly: ComVisible(true)]
+[assembly: ComVisible(false)]
 
 // The following GUID is for the ID of the typelib if this project is exposed to COM
 [assembly: Guid("07e68a3e-6ec7-4ee3-8904-013a6db77f79")]

SlimDucky.csproj

@@ -9,8 +9,9 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>SlimDucky</RootNamespace>
     <AssemblyName>SlimDucky</AssemblyName>
-    <TargetFrameworkVersion>v4.5.2</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
+    <TargetFrameworkProfile />
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
@@ -56,9 +57,11 @@
   <ItemGroup>
     <Compile Include="App.cs" />
     <Compile Include="Connect.cs" />
+    <Compile Include="DockableToolwindowPresenter.cs" />
     <Compile Include="DockableWindowHost.cs">
       <SubType>UserControl</SubType>
     </Compile>
+    <Compile Include="IDockableUserControl.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="SubclassingWindow.cs" />
     <Compile Include="SubClassingWindowEventArgs.cs" />

WinFormsControl.cs

@@ -1,20 +1,18 @@
-using System;
-using System.Collections.Generic;
-using System.ComponentModel;
-using System.Drawing;
-using System.Data;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using System.Windows.Forms;
+using System.Windows.Forms;
+using System.Runtime.InteropServices;
 
 namespace SlimDucky
 {
-    public partial class WinFormsControl : UserControl
+    [ComVisible(true)]
+    [Guid("AA0811DA-4C0E-45FE-A017-994298C675E5")]
+    public partial class WinFormsControl : UserControl, IDockableUserControl
     {
         public WinFormsControl()
         {
             InitializeComponent();
         }
+
+        public string ClassId => "AA0811DA-4C0E-45FE-A017-994298C675E5";
+        public string Caption => "WinForms ToolWindow";
     }
 }

WpfHostControl.cs

@@ -1,20 +1,18 @@
-using System;
-using System.Collections.Generic;
-using System.ComponentModel;
-using System.Drawing;
-using System.Data;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using System.Windows.Forms;
+using System.Windows.Forms;
+using System.Runtime.InteropServices;
 
 namespace SlimDucky
 {
-    public partial class WpfHostControl : UserControl
+    [ComVisible(true)]
+    [Guid("23D58F4F-FEE2-4D63-A5AE-EBBD360F26ED")]
+    public partial class WpfHostControl : UserControl, IDockableUserControl
     {
         public WpfHostControl()
         {
             InitializeComponent();
         }
+
+        public string ClassId => "23D58F4F-FEE2-4D63-A5AE-EBBD360F26ED";
+        public string Caption => "WPF ToolWindow";
     }
 }