There is only one easy and reliable way to get a valid Outlook object when dragging Outlook items onto a .NET form of your Outlook add-in. Let’s have a good look at this way by example of MailItem and an advanced Outlook form region.
So, we will need an instance of the advanced form region with TextBoxes in which we are going to display some MailItem properties. Set the AllowDrop property to true, and add two event handlers – DragOver and DragDrop.
In the DragOver event handler, check the Selection collection and make sure it contains a MailItem object (the code below is in VB.NET, a C# sample is available for download at the end of the post):
Private Sub ADXOlForm1_DragOver(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.DragEventArgs) _
Handles MyBase.DragOver
e.Effect = DragDropEffects.None
Dim selection As Outlook.Selection = TryCast(ExplorerObj, _
Outlook._Explorer).Selection
If selection IsNot Nothing Then
Try
If selection.Count = 1 Then
Dim mailItem As Outlook._MailItem = _
TryCast(selection.Item(1), Outlook._MailItem)
If mailItem IsNot Nothing Then
Try
e.Effect = DragDropEffects.All
Finally
Marshal.ReleaseComObject(mailItem)
End Try
End If
End If
Finally
Marshal.ReleaseComObject(selection)
End Try
End If
End Sub
In the DragDrop event handler, get the MailItem object from the Selection collection and fill in the TextBoxes with appropriate Outlook MailItem properties:
Private Sub ADXOlForm1_DragDrop(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.DragEventArgs) _
Handles MyBase.DragDrop
Dim selection As Outlook.Selection = TryCast(ExplorerObj, _
Outlook._Explorer).Selection
If selection IsNot Nothing Then
Try
Dim mailItem As Outlook._MailItem = _
TryCast(selection.Item(1), Outlook._MailItem)
If mailItem IsNot Nothing Then
Try
textBoxTo.Text = GetRecipients(mailItem, _
Outlook.OlMailRecipientType.olTo)
textBoxCC.Text = GetRecipients(mailItem, _
Outlook.OlMailRecipientType.olCC)
textBoxSubject.Text = mailItem.Subject
textBoxBody.Text = mailItem.Body
Finally
Marshal.ReleaseComObject(mailItem)
End Try
End If
Finally
Marshal.ReleaseComObject(selection)
End Try
End If
End Sub
That’s all with it. Have a good weekend!
You may also be interested in:
Advanced Outlook regions: Reading pane, Outlook bar, To-Do bar
Outlook plug-in development: toolbars, ribbons
Available downloads:
These sample add-ins were written on Add-in Express for Office and .net
C# sample Outlook add-in for VS 2005
VB.NET sample Outlook add-in for VS 2005
