在C＃中舍入一个数字很容易：
Math.Round(1.23456, 4); // returns 1.2346
但是，我想要舍入一个数字，使得数字的小数部分舍入到预定义分数的最接近的小数部分（例如1/8），并且我试图找出.NET库是否已经有这是内置的。
所以，例如，如果我想将十进制数舍入到整数八，那么我想调用类似的东西：
Math.RoundFractional(1.9, 8); // and have this yield 1.875
Math.RoundFractional(1.95, 8); // and have this yield 2.0
所以第一个参数是我要舍入的数字，第二个参数指示舍入分数。所以在这个例子中，在进行舍入后，小数点后面的数字只能是八个值中的一个：.000，.125，.250，.375，。500，.625，.750，.875
问题：这个功能是否在某个地方内置于.NET中？如果没有，是否有人有资源链接解释如何解决这个问题？
答案 0 :(得分：17)
你可以这样做：
Math.Round(n * 8) / 8.0
答案 1 :(得分：6)
不知道它是否内置于.NET中，但我只是这样做：
Math.Round(x * 8, 0) / 8;
将它四舍五入到最接近的第8位。
将您喜欢的号码替换为其他“分辨率”。
答案 2 :(得分：0)
这是一个较晚的答复，但对于任何正在寻找更全面的解决方案来转换原始文章所述的Double的人来说，这都是对的。下面是一个静态类，为双打提供了扩展方法，可以通过多种方式来实现此目的。
using System;
/// <summary>
/// Author: Aniceto Moreno Jr
/// Email: amorenojr@outlook.com
/// Date: 03/23/2020
/// </summary>
public static class DoubleExtensions
{
/// <summary>
/// Rounds the value to the nearest increment.
/// Assumes mid-point rounding, value >= 0.5 rounds up, value < 0.5 rounds down.
/// </summary>
/// <param name="Value"></param>
/// <param name="increment">Enter the increment value to round toward.</param>
/// <returns>Returns the value rounded to the nearest increment value.</returns>
public static double RoundToNearest(this double Value, double increment)
{
// Returning the value rounded to the nearest increment value.
return Math.Round(Value * Math.Pow(increment, -1), 0) * increment;
}
/// <summary>
/// Rounds down the value to the nearest increment.
/// </summary>
/// <param name="Value"></param>
/// <param name="increment">Enter the increment value to round down toward.</param>
/// <returns>Returns the value rounded down to the nearest increment value.</returns>
public static double FloorToNearest(this double Value, double increment)
{
// Returning the value rounded down to the nearest increment value.
return Math.Floor(Value * Math.Pow(increment, -1)) * increment;
}
/// <summary>
/// Rounds up the value to the nearest increment.
/// </summary>
/// <param name="Value"></param>
/// <param name="increment">Enter the increment value to round up toward.</param>
/// <returns>Returns the value rounded up to the nearest increment value.</returns>
public static double CeilingToNearest(this double Value, double increment)
{
// Returning the value rounded up to the nearest increment value.
return Math.Ceiling(Value * Math.Pow(increment, -1)) * increment;
}
/// <summary>
/// Rounds the value down to the nearest imperial fractional increment
/// and converts the value into an Inch-Fraction (IF) string.
/// Note: Assumes value is in inches and does not convert to Feet-Inch-Fraction (FIF)
/// </summary>
/// <param name="Value"></param>
/// <param name="maxDenominator">Enter the maximum denominator to round toward (i.e. 1/16 --> 16)</param>
/// <returns>Returns the value rounded down to the nearest increment value based on the maxDenominator.</returns>
public static string FloorToInchFraction(this double Value, int maxDenominator)
{
// Returning the rounded value converted into an Inch-Fraction (IF) string.
return Value.FloorToNearest(Math.Pow(maxDenominator, -1)).ToInchFraction(maxDenominator);
}
/// <summary>
/// Rounds the value up to the nearest imperial fractional increment
/// and converts the value into an Inch-Fraction (IF) string.
/// Note: Assumes value is in inches and does not convert to Feet-Inch-Fraction (FIF)
/// </summary>
/// <param name="Value"></param>
/// <param name="maxDenominator">Enter the maximum denominator to round toward (i.e. 1/16 --> 16)</param>
/// <returns>Returns the value rounded up to the nearest increment value based on the maxDenominator.</returns>
public static string CeilingToInchFraction(this double Value, int maxDenominator)
{
// Returning the rounded value converted into a fraction string.
return Value.CeilingToNearest(Math.Pow(maxDenominator, -1)).ToInchFraction(maxDenominator);
}
/// <summary>
/// Rounds the value to the nearest increment value based on the maximum denominator specified.
/// Assumes mid-point rounding, value >= 0.5 rounds up, value < 0.5 rounds down.
/// </summary>
/// <param name="Value"></param>
/// <param name="maxDenominator">Enter the maximum denominator to round toward (i.e. 1/16 --> 16)</param>
/// <returns>Returns the value rounded to the nearest increment value based on the maxDenominator.</returns>
public static string ToInchFraction(this double Value, int maxDenominator)
{
// Calculating the nearest increment of the value
// argument based on the denominator argument.
double incValue = Value.RoundToNearest(Math.Pow(maxDenominator, -1));
// Identifying the whole number of the argument value.
int wholeValue = (int)Math.Truncate(incValue);
// Calculating the remainder of the argument value and the whole value.
double remainder = incValue - wholeValue;
// Checking for the whole number case and returning if found.
if (remainder == 0.0) { return wholeValue.ToString() + (char)34; }
// Iterating through the exponents of base 2 values until the
// maximum denominator value has been reached or until the modulus
// of the divisor.
for (int i = 1; i < (int)Math.Log(maxDenominator, 2) + 1; i++)
{
// Calculating the denominator of the current iteration
double denominator = Math.Pow(2, i);
// Calculating the divisor increment value
double divisor = Math.Pow(denominator, -1);
// Checking if the current denominator evenly divides the remainder
if ((remainder % divisor) == 0.0) // If, yes
{
// Calculating the numerator of the remainder
// given the calculated denominator
int numerator = Convert.ToInt32(remainder * denominator);
// Returning the resulting string from the conversion.
return (wholeValue > 0 ? wholeValue.ToString() + "-" : "") + numerator.ToString() + "/" + ((int)denominator).ToString() + (char)34;
}
}
// Returns Error if something goes wrong.
return "Error";
}
/// <summary>
/// Rounds the value down to the nearest imperial fractional increment
/// and converts the value into an Feet-Inch-Fraction (FIF) string.
/// </summary>
/// <param name="Value"></param>
/// <param name="maxDenominator">Enter the maximum denominator to round toward (i.e. 1/16 --> 16)</param>
/// <returns>Returns the value rounded down to the nearest increment value based on the maxDenominator.</returns>
public static string FloorToFeetInchFraction(this double Value, int maxDenominator)
{
// Returning the rounded value converted into an Feet-Inch-Fraction (FIF) string.
return Value.FloorToNearest(Math.Pow(maxDenominator, -1)).ToFeetInchFraction(maxDenominator);
}
/// <summary>
/// Rounds the value up to the nearest imperial fractional increment
/// and converts the value into an Feet-Inch-Fraction (FIF) string.
/// </summary>
/// <param name="Value"></param>
/// <param name="maxDenominator">Enter the maximum denominator to round toward (i.e. 1/16 --> 16)</param>
/// <returns>Returns the value rounded up to the nearest increment value based on the maxDenominator.</returns>
public static string CeilingToFeetInchFraction(this double Value, int maxDenominator)
{
// Returning the rounded value converted into a fraction string.
return Value.CeilingToNearest(Math.Pow(maxDenominator, -1)).ToFeetInchFraction(maxDenominator);
}
/// <summary>
/// Rounds the value to the nearest increment value based on the maximum denominator specified.
/// Assumes mid-point rounding, value >= 0.5 rounds up, value < 0.5 rounds down.
/// </summary>
/// <param name="Value"></param>
/// <param name="maxDenominator">Enter the maximum denominator to round toward (i.e. 1/16 --> 16)</param>
/// <returns>Returns the value rounded to the nearest increment value based on the maxDenominator.</returns>
public static string ToFeetInchFraction(this double Value, int maxDenominator)
{
// Calculating the nearest increment of the value
// argument based on the denominator argument.
double incValue = Value.RoundToNearest(Math.Pow(maxDenominator, -1));
// Calculating the remainder of the argument value and the whole value.
double FeetInch = Math.Truncate(incValue) / 12.0;
// Calculating the remainder of the argument value and the whole value.
int Feet = (int)Math.Truncate(FeetInch);
// Calculating remaining inches.
incValue -= (double)(Feet * 12.0);
// Returns the feet plus the remaining amount converted to inch fraction.
return (Feet > 0 ? Feet.ToString() + (char)39 + " " : "") + incValue.ToInchFraction(maxDenominator);
}
}
使用和实施示例：
double testValue0 = 1.0625; // 1―1/16"
Console.WriteLine(testValue0.ToInchFraction(32)); // 1―1/16"
double testValue1 = 1.515625; // 1―33/64"
Console.WriteLine(testValue1.CeilingToInchFraction(16)); // 1―9/16"
double testValue2 = 1.03125; // 1―1/32"
Console.WriteLine(testValue2.FloorToInchFraction(16)); // 1"
double testValue3 = 5 / 25.4; // 5 mm = 0.1969 in
Console.WriteLine(testValue3.ToInchFraction(32)); // 3/16"
Console.WriteLine(testValue3.ToInchFraction(64)); // 13/64"