小数点位数

            //1.小数点位数
            string str1 = String.Format("{0:F1}", 56789); //result: 56789.0
            string str2 = String.Format("{0:F2}", 56789); //result: 56789.00
            string str3 = String.Format("{0:N1}", 56789); //result: 56,789.0
            string str4 = String.Format("{0:N2}", 56789); //result: 56,789.00
            string str5 = String.Format("{0:N3}", 56789); //result: 56,789.000
            string str6 = (56789 / 100.0).ToString("#.##"); //result: 567.89
            string str7 = (56789 / 100).ToString("#.##"); //result: 567

            //2.保留N位,四舍五入 .       
            decimal d = decimal.Round(decimal.Parse("0.55555"), 2);//0.56

            //3.保留N位四舍五入
           var r =  Math.Round(0.55555, 2);//0.56