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.

Answer 1

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.