Outlook 2010 issue. Drag-n-drop onto a custom task pane causes Selection.Count to grow

Question

Hello,

We have an issue reported by our customer. I reproduced the issue in the project described below.

The project. The project is downloadable here, file size = 16 969. This is an Outlook 2010 add-in project in VSTO 2010. The code in ThisAddin.vb:

Public Class ThisAddIn
    Private WithEvents explorer As Outlook.Explorer
    Private ctp As Microsoft.Office.Tools.CustomTaskPane

    Private Sub ThisAddIn_Startup() Handles Me.Startup
        explorer = Application.ActiveExplorer()
        ctp = Me.CustomTaskPanes.Add(New UserControl1(), "Title")
        ctp.DockPosition = Microsoft.Office.Core.MsoCTPDockPosition.msoCTPDockPositionRight
        ctp.Visible = True
    End Sub

    Private Sub ThisAddIn_Shutdown() Handles Me.Shutdown
        Me.CustomTaskPanes.Remove(ctp)
        System.Runtime.InteropServices.Marshal.ReleaseComObject(explorer)
    End Sub

    Private Sub explorer_SelectionChange() Handles explorer.SelectionChange
        Dim selection As Outlook.Selection = explorer.Selection
        System.Diagnostics.Debug.WriteLine("!!! selection.Count=" + selection.Count.ToString())
        Dim res As Integer
        res = System.Runtime.InteropServices.Marshal.ReleaseComObject(selection)
        System.Diagnostics.Debug.WriteLine("!!! res=" + res.ToString())
    End Sub
End Class

UserControl1.vb

Public Class UserControl1

    Private Sub UserControl1_DragEnter(sender As System.Object, e As System.Windows.Forms.DragEventArgs) Handles MyBase.DragEnter
        e.Effect = Windows.Forms.DragDropEffects.All
    End Sub

    Private Sub UserControl1_DragDrop(sender As System.Object, e As System.Windows.Forms.DragEventArgs) Handles MyBase.DragDrop

    End Sub
End Class

InitializeComponent in UserControl1.Designer.vb:

    <System.Diagnostics.DebuggerStepThrough()> _
    Private Sub InitializeComponent()
        Me.SuspendLayout()
        '
        'UserControl1
        '
        Me.AllowDrop = True
        Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
        Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
        Me.Name = "UserControl1"
        Me.ResumeLayout(False)

    End Sub

The issue. Start Outlok 2010 SP 1 32-bit. In the explorer window, drag an item onto the custom task pane; you may be required to drop one more item. Now start selecting items and check the selection.Count. The result: selection.Count grows while you select new items. The expected behavior: selection.Count should return the number of items actually selected in the explorer.

In my tests, the Navigation pane was Normal, the To-Do Bar was Normal, the Reading pane was Off.

Note. If the Reading Pane is shown, it freezes after drag-n-drop. Because we reported the Outlook team about Reading Pane freezing after drag-n-drop in Outlook 2010 32-bit a while back, the current issue seems to be just another manifestation of the same bug. However, I didn't test the current issue in Outlook 2010 64-bit, sorry.

---

Regards from Belarus (GMT + 2),

Andrei Smolin
Add-in Express Team Leader

Answer 1

Hi Andrei.  I've notified the product team.

---

Eric Legault
MVP (Outlook)
About me...

Answer 2

Hi Eric,

 

Would you please share the Connect link for us? It will be very beneficial for all of the community members who interesting in it to track the process of it.

 

Have a good day,

 

Tom

---

Tom Xu [MSFT]
MSDN Community Support | Feedback to us
Get or Request Code Sample from Microsoft
Please remember to mark the replies as answers if they help and unmark them if they provide no help.

Answer 3

I was never given a Connect link, as I don't think the Outlook team ever files anything there.  I was told that it's a known issue.  You can follow up with Teresa Thomas if you like.

---

Eric Legault
MVP (Outlook)
About me...

Answer 4

Hi Eric,

Thanks for your clarify.

Have a good day,

Tom

---

Tom Xu [MSFT]
MSDN Community Support | Feedback to us
Get or Request Code Sample from Microsoft
Please remember to mark the replies as answers if they help and unmark them if they provide no help.

Answer 5

Hello everyone,

We've found a solution for this problem. Find a shared add-in project demonstrating the solution in Outlook, custom task pane and drag-drop problem on the Add-in Express blog.

---

Regards from Belarus (GMT + 3),

Andrei Smolin
Add-in Express Team Leader

Please mark answers and useful posts to help other developers use the forums efficiently.