double dValue = 99.123456; int iValue = 9999; string strValue = "99.123456"; string result = ""; result = dValue.ToString("0.00");//99.12 result = Convert.ToDouble(iValue).ToString("0.00");//9999.00 result = Convert.ToDouble(strValue).ToString("0.00"); //99.12 //得到小数点后2位的百分比,自动 加上%号; result = Convert.ToDouble(dValue).ToString("P"); //9912.34% //保留小数点后3位; result = Convert.ToDouble(strValue).ToString("f3"); //99.123