如何围捕（没有上限）在C＃：N.5达（+）无限

Question

如问题，如何围捕中C#与n.5值（n为整数）：

1.5 -> 2 
2.5 -> 3 
-1.5 -> -1 
-2.5 -> -2 

1.4 -> 1 
1.6 -> 2 
-1.4 -> -1 
-1.6 -> -2 

我搜索但在C#,Math.Round只支持MidpointRounding.AwayFromZero和MidpointRounding.ToEven。也许程序员应该做把戏在正常的生活思想（不是银行业或学术思想......）中围绕一个数字？

也就是说预期的结果是在Javascript，价值N.5总是四舍五入到（+）无限 +∞

Answer 1

试试这个:)

[TestFixture] 
public class TestClass 
{ 
    int NumberOfDecimalDigits(double d) 
    { 
     var text = Math.Abs(d).ToString(); 
     int integerPlaces = text.IndexOf('.'); 
     int decimalPlaces = text.Length - integerPlaces - 1; 
     return decimalPlaces; 
    } 

    double GetDelta(int numberOfDecimalDigits) 
    { 
     var deltaStringBuilder = new StringBuilder(); 
     deltaStringBuilder.Append("1"); 
     for (int i = 0; i < numberOfDecimalDigits; i++) 
     { 
      deltaStringBuilder.Append("0"); 
     } 


     double delta = 1/double.Parse(deltaStringBuilder.ToString()); 
     return delta; 
    } 

double Round(double value, int digits) 
     { 
      if (value > 0) 
      { 
       return Math.Round(value, digits, MidpointRounding.AwayFromZero); 
      } 
      if (value < 0) 
      { 
       var numberOfDecimalDigits = NumberOfDecimalDigits(value); 
       double delta = GetDelta(numberOfDecimalDigits); 
       return Math.Round(value + delta, digits, MidpointRounding.AwayFromZero); 
      } 

      return value; 
     } 

    double Round(double value) 
    { 
     if (value > 0) 
     { 
      return Math.Round(value, MidpointRounding.AwayFromZero); 
     } 
     if (value < 0) 
     { 
      var numberOfDecimalDigits = NumberOfDecimalDigits(value); 
      double delta = GetDelta(numberOfDecimalDigits); 
      return Math.Round(value + delta, MidpointRounding.AwayFromZero); 
     } 

     return value; 
    } 
    [Test] 
    public void TestMethod() 
    { 
     Assert.AreEqual(Round(1), 1); 
     Assert.AreEqual(Round(1.9), 2); 
     Assert.AreEqual(Round(1.5), 2); 
     Assert.AreEqual(Round(2.5), 3); 

     Assert.AreEqual(Round(-1), -1); 
     Assert.AreEqual(Round(-2.9), -3); 

     Assert.AreEqual(Round(-1.5), -1); 
     Assert.AreEqual(Round(-2.5), -2); 
     Assert.AreEqual(Round(1.4), 1); 
     Assert.AreEqual(Round(1.6), 2); 

     Assert.AreEqual(Round(-1.4), -1); 
     Assert.AreEqual(Round(-1.6), -2); 
     Assert.AreEqual(Round(-1.55), -2); 

     Assert.AreEqual(Round(-1.6666), -2); 
     Assert.AreEqual(Round(-0.9999999), -1); 
     Assert.AreEqual(Round(-0.001), 0); 

     Assert.AreEqual(Round(2.35, 1), 2.4); 
     Assert.AreEqual(Round(-2.35, 1), -2.3); 

    } 

Answer 2

下面是其通过一个版本所有测试用例。

static void Main(string[] args) 
    { 
     Round(double.Epsilon, 0); 
     Round(0-double.Epsilon, 0); 

     Round(1 + double.Epsilon, 1); 
     Round(1 - double.Epsilon, 1); 


     Round(1.5, 2); 
     Round(2.5, 3); 
     Round(-1.5, -1); 
     Round(-2.5, -2); 

     Round(1.4, 1); 
     Round(1.6, 2); 
     Round(-1.4, -1); 
     Round(-1.6, -2); 
    } 

    private static void Round(double v1, int v2) 
    { 
     var equal = (MyRound(v1) == v2) ? "==" : "!="; 
     Console.WriteLine($"Math.Round({v1}) {equal} {v2}, it's {MyRound(v1)}"); 
    } 

    private static double MyRound(double v1) 
    { 
     return (v1 < 0) 
      ? 0 - Math.Round(Math.Abs(v1)-0.1) 
      : Math.Round(v1, MidpointRounding.AwayFromZero); 
    } 

输出：

Math.Round(4.94065645841247E-324) == 0, it's 0 
Math.Round(-4.94065645841247E-324) == 0, it's 0 
Math.Round(1) == 1, it's 1 
Math.Round(1) == 1, it's 1 
Math.Round(1.5) == 2, it's 2 
Math.Round(2.5) == 3, it's 3 
Math.Round(-1.5) == -1, it's -1 
Math.Round(-2.5) == -2, it's -2 
Math.Round(1.4) == 1, it's 1 
Math.Round(1.6) == 2, it's 2 
Math.Round(-1.4) == -1, it's -1 
Math.Round(-1.6) == -2, it's -2