1         private int GetLineNoVscroll(RichTextBox rtb)
2         {
3             //获得当前坐标信息
4             Point p = rtb.Location;
5             int crntFirstIndex = rtb.GetCharIndexFromPosition(p);
6             int crntFirstLine = rtb.GetLineFromCharIndex(crntFirstIndex);
7             return crntFirstLine;
8         }

 1   private void TrunRowsId(int iCodeRowsID, RichTextBox rtb)
 2         {
 3             try
 4             {
 5                 rtb.SelectionStart = rtb.GetFirstCharIndexFromLine(iCodeRowsID);
 6                 rtb.SelectionLength = 0;
 7                 rtb.ScrollToCaret();
 8             }
 9             catch
10             {
11 
12             }
13         }

1         private void richTextBox1_VScroll(object sender, EventArgs e)
2         {
             int wucha=0;
3            int crntLastLine= GetLineNoVscroll(richTextBox1, panel1)-wucha;
4             TrunRowsId(crntLastLine, richTextBox2);
5         }