VB.Net Drag and Drop from Outlook

One thing I have been working on for years now is a database program that among other things has a part that lets you attach files into it. The drag and drop functionality was easy for regular files on the hard drive but a feature request came in to drag and drop files from a outlook attachment. Luckily someone had already figured this out in C# which I converted into VB here: http://www.codeproject.com/Articles/7140/Drag-and-Drop-Attached-File-From-Outlook-and-ab. This was all fine and dandy until I got a request last week to attach the actual email itself, not a attachment. After more searching I found someone that did this using the Outlook interop libraries here: http://www.emoreau.com/Entries/Articles/2008/05/Dropping-a-Outlook-message-on-your-application.aspx. So after a little more playing I updated my drag and drop code to decipher between a normal file, a Outlook attachment, or a Outlook email and act accordingly.

Couple notes: DisplayMessageBox is a custom message box used by my program (replace with MsgBox if needed) and AddTempFileToArray does exactly that, adds any temp files I create or use to a array which I then delete when my program closes (don’t want a bunch of temp files created and left), and SaveButton is enabled only during a edit operation.

In my control where I will accept the drop:

Private Sub MyControlToAcceptTheDrop_DragEnter(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles MyControlToAcceptTheDrop.DragEnter
' Make sure that the format is a file drop.
If (e.Data.GetDataPresent(DataFormats.FileDrop)) And (SaveButton.Visible = True) Then
e.Effect = DragDropEffects.Copy
ElseIf (e.Data.GetDataPresent("FileGroupDescriptor")) And (SaveButton.Visible = True) Then
e.Effect = DragDropEffects.Copy
Else
' Do not allow drop.
e.Effect = DragDropEffects.None
End If
End Sub

And my code to handle the drop:

'''

''' Handle File Drops
'''

''' DragEventArgs ''' Path to the actual file or temp file
''' Returns the full path to the file being dropped or to a temp file that contains the file in memory (for use with Outlook or other program drag drops)
Friend Function HandleFileDrops(ByVal e As System.Windows.Forms.DragEventArgs) As String
Try
If e.Data.GetDataPresent(DataFormats.FileDrop) Then
' We have a file so lets pass it to the calling form
Dim Filename As String() = CType(e.Data.GetData(DataFormats.FileDrop), String())
HandleFileDrops = Filename(0)
ElseIf e.Data.GetDataPresent("FileGroupDescriptor") Then
' We have a embedded file. First lets try to get the file name out of memory
Dim theStream As Stream = CType(e.Data.GetData("FileGroupDescriptor"), Stream)
Dim fileGroupDescriptor(512) As Byte
theStream.Read(fileGroupDescriptor, 0, 512)
Dim fileName As System.Text.StringBuilder = New System.Text.StringBuilder("")
Dim i As Integer = 76
While Not (fileGroupDescriptor(i) = 0)
fileName.Append(Convert.ToChar(fileGroupDescriptor(i)))
System.Math.Min(System.Threading.Interlocked.Increment(i), i - 1)
End While
theStream.Close()
' We should have the file name or if its a email the subject line. Create our temp file based on the temp path and this info
Dim myTempFile As String = Path.GetTempPath & fileName.ToString
' Look to see if this is a email message. If so save that temporarily and get the temp file.
If InStr(myTempFile, ".msg") > 0 Then
Dim objOL As New Microsoft.Office.Interop.Outlook.Application
Dim objMI As Microsoft.Office.Interop.Outlook.MailItem
If objOL.ActiveExplorer.Selection.Count > 1 Then
DisplayMessageBox("You can only drag and drop one item at a time into this screen. The first item you selected will be used.", "One Item At A Time", , FormStartPosition.CenterParent)
End If
For Each objMI In objOL.ActiveExplorer.Selection()
objMI.SaveAs(myTempFile)
Exit For
Next
objOL = Nothing
objMI = Nothing
Else
' If its a attachment we need to pull the file itself out of memory
Dim ms As MemoryStream = CType(e.Data.GetData("FileContents", True), MemoryStream)
Dim FileBytes(CInt(ms.Length)) As Byte
' read the raw data into our variable
ms.Position = 0
ms.Read(FileBytes, 0, CInt(ms.Length))
ms.Close()
' save the raw data into our temp file
Dim fs As FileStream = New FileStream(myTempFile, FileMode.OpenOrCreate, FileAccess.Write)
fs.Write(FileBytes, 0, FileBytes.Length)
fs.Close()
End If
' Make sure we have a actual file and also if we do make sure we erase it when done
If File.Exists(myTempFile) Then
' Assign the file name to the add dialog
HandleFileDrops = myTempFile
Call AddTempFileToArray(myTempFile)
Else
HandleFileDrops = String.Empty
End If
Else
Throw New System.Exception("An exception has occurred.")
End If
Catch ex As Exception
DisplayMessageBox("Could not copy file from memory. Please save the file to your hard drive first and then retry your drag and drop.", "Drag and Drop Failed")
HandleFileDrops = String.Empty
End Try

End Function

As you might be able to guess I only look at the first email message if multiple are selected and let the user know that also. I’m sure there is a way to loop through multiple files, Outlook attachments, or Outlook emails but I don’t need that functionality so I didn’t code it (but I did warn in case it happens).

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