Option Explicit On 
Option Strict Off ' Using late binding.

Imports System
Imports EnvDTE
Imports System.Diagnostics

Public Module Module1

  Private Const WdPasteDefault As Integer = 0
  Private Const WdFormatFilteredHTML As Integer = 10
  Private Const WdWebView As Integer = 6

  Sub FormatSourceCode()

    ' Get the currently selected code snippet.
    Dim selection As TextSelection = CType(DTE.ActiveDocument.Selection(), TextSelection)

    ' Check that something is selected.
    If selection.Text = "" Then
      MsgBox("No code selected!", MsgBoxStyle.Critical Or MsgBoxStyle.OKOnly, "Format Code")
      Return
    End If

    ' Create a temporary file.
    Dim path As String = System.IO.Path.GetTempFileName()

    ' Copy the selected code to clipboard (using VS.NET).
    selection.Copy()

    ' Instantiate a new Word document to achieve HTML code formatting.
    Dim oleDocument As Type = Type.GetTypeFromProgID("Word.Document")
    Dim document As Object = Activator.CreateInstance(oleDocument)
    document.ActiveWindow.Selection.PasteAndFormat(WdPasteDefault)
    document.SaveAs(path, WdFormatFilteredHTML, False, "", True, "", False, False, False, False, False)
    document.Close()
    document = Nothing
    oleDocument = Nothing
 
    ' Open a new instance of Word.
    Dim oleApplication As Type = Type.GetTypeFromProgID("Word.Application")
    Dim application As Object = Activator.CreateInstance(oleApplication)
    ' Open the temporary document.
    document = application.Documents.Open(path)
    ' Switch to the WebView mode within Word.
    document.ActiveWindow.View.Type = WdWebView
    ' Select the whole document.
    document.ActiveWindow.Selection.WholeStory()
    ' Copy it to the clipboard.
    document.ActiveWindow.Selection.Copy()
    ' Close the document.
    document.Close()
    document = Nothing
    application.Quit()
    application = Nothing
    oleApplication = Nothing
 
    ' Cleanup after ourselves.
    IO.File.Delete(path)
 
  End Sub
 
End Module