Capture CTRL+V or paste in a textbox in .NET

Question

VB.NET 2010 - I have a RichTextbox in which the user can manually enter data or copy/paste from another source. After the data is complete he hits go and a few key words are highlighted. My issue is that if he copy/pastes from another source the formatting also gets copied. Well sometimes the outside source has a white font and my textbox has a white background so it appears like he pasted nothing and he does it again and again.

What I'm looking for is a way to intercept the paste action into the textbox so that I can take that text and paste it as pure ASCII without formatting.

Edit after experimenting with KeyDown

Private Sub txtRch_KeyDown(sender As Object, e As System.Windows.Forms.KeyEventArgs) Handles txtRch.KeyDown
    If e.Modifiers = Keys.Control AndAlso e.KeyCode = Keys.V Then
        With txtRch
            Dim i As Integer = .SelectionStart          'cache the current position
            .Select(0, i)                               'select text from start to current position
            Dim s As String = .SelectedText             'copy that text to a variable
            .Select(i, .TextLength)                     'now select text from current position to end
            Dim t As String = .SelectedText             'copy that text to a variable
            Dim u As String = s & Clipboard.GetText(TextDataFormat.UnicodeText) & t 'now concatenate the first chunk, the new text, and the last chunk
            .Clear()                                    'clear the textbox
            .Text = u                                   'paste the new text back into textbox
            .SelectionStart = i                         'put cursor back to cached position
        End With

        'the event has been handled manually
        e.Handled = True
    End If
End Sub

This seems to work and all my text gets retained and its all ASCII. I think if I wanted to take a step further I could also take the font and forecolor of my RichTextbox, select all text, and then assign the font and forecolor to the selection.

Solution

In most cases, examining the KeyDown event should be good enough along with using a temporary RichTextBox to modify the incoming text:

Private Sub RichTextBox1_KeyDown(sender As Object, e As KeyEventArgs) _
                                 Handles RichTextBox1.KeyDown
  If e.Modifiers = Keys.Control AndAlso e.KeyCode = Keys.V Then

    Using box As New RichTextBox
      box.SelectAll()
      box.SelectedRtf = Clipboard.GetText(TextDataFormat.Rtf)
      box.SelectAll()
      box.SelectionBackColor = Color.White
      box.SelectionColor = Color.Black
      RichTextBox1.SelectedRtf = box.SelectedRtf
   End Using

   e.Handled = True
  End If
End Sub

Note: Missing any error checking.