tx.cs

private void textControl1_KeyDown(object sender, KeyEventArgs e)
{
    if (e.Control && e.KeyCode == Keys.Delete)
    {
        // get the current paragraph at the input position
        TXTextControl.Paragraph curParagraph =
            textControl1.Paragraphs.GetItem(textControl1.Selection.Start);
        
        // return the text beginning at the input position
        // until the end of the paragraph
        string sParagraph = curParagraph.Text.Substring(
            textControl1.Selection.Start - curParagraph.Start + 1);

        // search for delimiters and return the positions
        List<int> indexes = Regex.Matches(sParagraph, @"[^\w]+").Cast<Match>()
                .Select(m => m.Index)
                .ToList();

        // if delimiters are found, select the text until the next
        // delimiter and remove the text
        if (indexes.Count > 0)
        {
            textControl1.Selection.Length = indexes[0] + 1;
            textControl1.Selection.Text = "";

            // cancel the original event handling
            e.Handled = true;
        }
    }
}