获取有效位数

获取有效位数，当是小数时可以使用；

        /// <summary>
        /// 小数获取有效位数
        /// </summary>
        /// <param name="dvalue">数值</param>
        /// <param name="digit">位数</param>
        /// <returns>返回值</returns>
        public static double EffectiveValue(double dvalue, int digit)
        {
            if (dvalue == 0.0) return 0;
            if (dvalue > 1 || dvalue < -1)
                digit = digit - (int)Math.Log10(Math.Abs(dvalue)) - 1;
            else
                digit = digit + (int)Math.Log10(1.0 / Math.Abs(dvalue));
            if (digit < 0)
            {
                dvalue = (int)(dvalue / Math.Pow(10, 0 - digit)) * Math.Pow(10, 0 - digit);
                digit = 0;
            }
            return Math.Round(dvalue, digit);
        }

 获取到小数点后 digit 位有效数字

        /// <summary>
        /// 获取有效位数
        /// </summary>
        /// <param name="dvalue">数值</param>
        /// <param name="digit">位数</param>
        /// <returns>返回值</returns>
        public static decimal DoubleEffectiveValue(decimal dvalue, int digit)
        {

            decimal dint = decimal.Truncate(dvalue);
            decimal dxiaoshuo = dvalue - dint;   //小数位
            if (dxiaoshuo == 0) return dint;
            digit = digit + (int)Math.Log10(1.0 / Math.Abs(Convert.ToDouble(dxiaoshuo)));
            return decimal.Round(dvalue, digit);  
        }