private void OnTextFind()
{
string strNeedle = m_tbFind.Text;
if(string.IsNullOrEmpty(strNeedle)) return;
int iStart = m_rtbText.SelectionStart + m_rtbText.SelectionLength;
if(iStart < 0) { Debug.Assert(false); iStart = 0; }
if(iStart >= m_rtbText.TextLength) iStart = 0;
int p = m_rtbText.Find(strNeedle, iStart, -1, RichTextBoxFinds.None);
if(p < 0) m_rtbText.Find(strNeedle, 0, -1, RichTextBoxFinds.None);
}