public static double Round(double d, int i)         {             if (d >= 0)             {                 d += 5 * Math.Pow(10, -(i + 1));//求指定次数的指定次幂             }             else             {                 d += 5 * Math.Pow(10, -(i + 1));             }             string str = d.ToString();             string[] strs = str.Split('.');             int idot = str.IndexOf('.');             string prestr = strs[0];             string poststr = strs[1];             if (poststr.Length > i)             {                 poststr = str.Substring(idot + 1, i);//截取需要位数             }             if (poststr.Length <= 2)             {                 poststr = poststr + "0";             }             string strd = prestr + "." + poststr;             d = double.Parse(strd);//将字符串转换为双精度实数             return d;         }         private void button1_Click(object sender, EventArgs e)         {             textBox3.Text=Convert.ToString(Math.Round(Convert.ToDouble(textBox1.Text.Trim()),Convert.ToInt16(textBox2.Text.Trim())));         }