c#中richtextbox显示不同的颜色

List strWarn=new List();//定义一个泛型，可以自由的添加字段

private void WarnInfo(string str)
       {
           strWarn.Add(str);
           for (int i = 0; i < strWarn.Count; i++)
           {
               int lenth = richTextBox1.Text.Length;
               richTextBox1.AppendText(strWarn[i]);
               if (richTextBox1.Lines[i].Contains("一级警告"))
               {
                   for (int j = 0; strWarn[i][j] != '\n'; j++)//对于这一行来说\n是结尾
                   {
                       richTextBox1.Select(lenth + j, 1);//一个一个的选择然后改变颜色
                       richTextBox1.SelectionColor = Color.Red;
                   }
               }
               if (richTextBox1.Lines[i].Contains("二级警告"))
               {
                   for (int j = 0; strWarn[i][j] != '\n'; j++)
                   {
                       richTextBox1.Select(lenth + j, 1);
                       richTextBox1.SelectionColor = Color.Orange;
                   }
               }
          }
       }

当需要滚动显示出来的信息都是显示最后的信息可以附加：

private void richTextBox1_TextChanged(object sender, EventArgse)
       {
           richTextBox1.SelectionStart = richTextBox1.TextLength;
           // Scrolls the contents of the control to the current caretposition.
           richTextBox1.ScrollToCaret();

       }