http://msdn2.microsoft.com/en-us/library/bb175107.aspx

How can I convert this VBA code to C# or VB.NET by using Visual Studio 2005
Professional edition, shared add-in?

How can I define AttachmentContextMenuDisplay(CommandBar, Attachments) event
in OnStartupComplete(...) part or where ?

VBA Code:

Private Declare Function SHGetSpecialFolderLocation _
Lib "shell32" (ByVal hWnd As Long, _
ByVal nFolder As Long, ppidl As Long) As Long

Private Declare Function SHGetPathFromIDList _
Lib "shell32" Alias "SHGetPathFromIDListA" _
(ByVal Pidl As Long, ByVal pszPath As String) As Long

Private Declare Sub CoTaskMemFree Lib "ole32" (ByVal pvoid As Long)

Dim objAttachments As AttachmentSelection

Private Sub Application_AttachmentContextMenuDisplay( _
ByVal CommandBar As Office.CommandBar, _
ByVal Attachments As AttachmentSelection)

Dim objButton As CommandBarButton

On Error GoTo ErrRoutine

If Attachments.Count 0 Then

' Get a reference to the selected attachments
' so we can work with them in the
' SaveToDesktop routine.
Set objAttachments = Attachments

' Create a new menu item and place it
' just after the Reply To All button
Set objButton = CommandBar.Controls.Add( _
msoControlButton, , , , True)

' Configure the menu item.
With objButton
.Style = msoButtonIconAndCaption
.Caption = "Save to &Desktop"
.FaceId = 355
' If you place this sample in a class module
' other than ThisOutlookSession, update this
' line of code to ensure that the OnAction
' property contains the correct project,
' class, and routine name.
.OnAction = "Project1.ThisOutlookSession.SaveToDesktop"
End With
End If

EndRoutine:
On Error GoTo 0
Set objButton = Nothing
Exit Sub

ErrRoutine:
MsgBox Err.Number & " - " & Err.Description, _
vbOKOnly Or vbCritical, _
"Application_AttachmentContextMenuDisplay"
GoTo EndRoutine
End Sub

Private Sub SaveToDesktop()
Dim lngPidlFound As Long
Dim lngFolderFound As Long
Dim lngPidl As Long
Dim strPath As String
Dim objAttachment As Attachment

Const CSIDL_DESKTOPDIRECTORY = &H10
Const MAX_PATH = 260
Const NOERROR = 0

On Error GoTo ErrRoutine

' Obtain the physical path to the desktop folder
' for the current user.
strPath = Space(MAX_PATH)
lngPidlFound = SHGetSpecialFolderLocation( _
0, CSIDL_DESKTOPDIRECTORY, lngPidl)

If lngPidlFound = NOERROR Then
lngFolderFound = SHGetPathFromIDList(lngPidl, strPath)
If lngFolderFound Then
strPath = Left$(strPath, _
InStr(1, strPath, vbNullChar) - 1)
If Right(strPath, 1) "\" Then strPath = strPath & "\"
End If
End If

CoTaskMemFree lngPidl

' Save each selected attachment to the
' desktop folder.
If strPath "" Then
For Each objAttachment In objAttachments
objAttachment.SaveAsFile strPath & objAttachment.FileName
Next
End If

EndRoutine:
On Error GoTo 0
Set objAttachment = Nothing
Exit Sub

ErrRoutine:
MsgBox Err.Number & " - " & Err.Description, _
vbOKOnly Or vbCritical, _
"SaveToDesktop"
GoTo EndRoutine
End Sub

Private Sub Application_ContextMenuClose(ByVal ContextMenu As OlContextMenu)
On Error Resume Next

If ContextMenu = olAttachmentContextMenu Then
' Once the context menu closes, remove the
' object reference to the attachments.
If Not (objAttachments Is Nothing) Then
Set objAttachments = Nothing
End If
End If

On Error GoTo 0
End Sub