.NET 单位等级，英寸到毫米

Question

.NET 有单位转换类吗？我需要将英寸转换为毫米，反之亦然。

Answer 1

不，没有类似的内置功能。但您可以简单地乘或除以 25.4。

Answer 2

我以前处理过这个问题。我建议针对距离开设两门课程。一种具有英制尺寸，一种具有公制尺寸。然后，您可以轻松地在它们之间来回转换，但需要注意的是，这样做时会失去精度。

以下是英制距离等级的示例，以英寸为基本测量单位。

public class ImperialDistance
{
    public static readonly ImperialDistance Inch = new ImperialDistance(1.0);
    public static readonly ImperialDistance Foot = new ImperialDistance(12.0);
    public static readonly ImperialDistance Yard = new ImperialDistance(36.0);
    public static readonly ImperialDistance Mile = new ImperialDistance(63360.0);

    private double _inches;

    public ImperialDistance(double inches)
    {
        _inches = inches;
    }

    public double ToInches()
    {
        return _inches;
    }

    public double ToFeet()
    {
        return _inches / Foot._inches;
    }

    public double ToYards()
    {
        return _inches / Yard._inches;
    }

    public double ToMiles()
    {
        return _inches / Mile._inches;
    }

    public MetricDistance ToMetricDistance()
    {
        return new MetricDistance(_inches * 0.0254);
    }

    public override int GetHashCode()
    {
        return _inches.GetHashCode();
    }

    public override bool Equals(object obj)
    {
        var o = obj as ImperialDistance;
        if (o == null) return false;
        return _inches.Equals(o._inches);
    }

    public static bool operator ==(ImperialDistance a, ImperialDistance b)
    {
        // If both are null, or both are same instance, return true
        if (ReferenceEquals(a, b)) return true;

        // if either one or the other are null, return false
        if (ReferenceEquals(a, null) || ReferenceEquals(b, null)) return false;

        // compare
        return a._inches == b._inches;
    }

    public static bool operator !=(ImperialDistance a, ImperialDistance b)
    {
        return !(a == b);
    }

    public static ImperialDistance operator +(ImperialDistance a, ImperialDistance b)
    {
        if (a == null) throw new ArgumentNullException();
        if (b == null) throw new ArgumentNullException();
        return new ImperialDistance(a._inches + b._inches);
    }

    public static ImperialDistance operator -(ImperialDistance a, ImperialDistance b)
    {
        if (a == null) throw new ArgumentNullException();
        if (b == null) throw new ArgumentNullException();
        return new ImperialDistance(a._inches - b._inches);
    }

    public static ImperialDistance operator *(ImperialDistance a, ImperialDistance b)
    {
        if (a == null) throw new ArgumentNullException();
        if (b == null) throw new ArgumentNullException();
        return new ImperialDistance(a._inches * b._inches);
    }

    public static ImperialDistance operator /(ImperialDistance a, ImperialDistance b)
    {
        if (a == null) throw new ArgumentNullException();
        if (b == null) throw new ArgumentNullException();
        return new ImperialDistance(a._inches / b._inches);
    }
}

这是一个以米为基本单位的度量类：

public class MetricDistance
{
    public static readonly MetricDistance Milimeter  = new MetricDistance(0.001);
    public static readonly MetricDistance Centimeter = new MetricDistance(0.01);
    public static readonly MetricDistance Decimeter  = new MetricDistance(0.1);
    public static readonly MetricDistance Meter      = new MetricDistance(1.0);
    public static readonly MetricDistance Decameter  = new MetricDistance(10.0);
    public static readonly MetricDistance Hectometer = new MetricDistance(100.0);
    public static readonly MetricDistance Kilometer  = new MetricDistance(1000.0);

    private double _meters;

    public MetricDistance(double meters)
    {
        _meters = meters;
    }

    public double ToMilimeters()
    {
        return _meters / Milimeter._meters;
    }

    public double ToCentimeters()
    {
        return _meters / Centimeter._meters;
    }

    public double ToDecimeters()
    {
        return _meters / Decimeter._meters;
    }

    public double ToMeters()
    {
        return _meters;
    }

    public double ToDecameters()
    {
        return _meters / Decameter._meters;
    }

    public double ToHectometers()
    {
        return _meters / Hectometer._meters;
    }

    public double ToKilometers()
    {
        return _meters / Kilometer._meters;
    }

    public ImperialDistance ToImperialDistance()
    {
        return new ImperialDistance(_meters * 39.3701);
    }

    public override int GetHashCode()
    {
        return _meters.GetHashCode();
    }

    public override bool Equals(object obj)
    {
        var o = obj as MetricDistance;
        if (o == null) return false;
        return _meters.Equals(o._meters);
    }

    public static bool operator ==(MetricDistance a, MetricDistance b)
    {
        // If both are null, or both are same instance, return true
        if (ReferenceEquals(a, b)) return true;

        // if either one or the other are null, return false
        if (ReferenceEquals(a, null) || ReferenceEquals(b, null)) return false;

        return a._meters == b._meters;
    }

    public static bool operator !=(MetricDistance a, MetricDistance b)
    {
        return !(a == b);
    }

    public static MetricDistance operator +(MetricDistance a, MetricDistance b)
    {
        if (a == null) throw new ArgumentNullException("a");
        if (b == null) throw new ArgumentNullException("b");
        return new MetricDistance(a._meters + b._meters);
    }

    public static MetricDistance operator -(MetricDistance a, MetricDistance b)
    {
        if (a == null) throw new ArgumentNullException("a");
        if (b == null) throw new ArgumentNullException("b");
        return new MetricDistance(a._meters - b._meters);
    }

    public static MetricDistance operator *(MetricDistance a, MetricDistance b)
    {
        if (a == null) throw new ArgumentNullException("a");
        if (b == null) throw new ArgumentNullException("b");
        return new MetricDistance(a._meters * b._meters);
    }

    public static MetricDistance operator /(MetricDistance a, MetricDistance b)
    {
        if (a == null) throw new ArgumentNullException("a");
        if (b == null) throw new ArgumentNullException("b");
        return new MetricDistance(a._meters / b._meters);
    }
}

这是一个示例用法的测试方法。

[TestMethod]
public void _5in_Equals_12_7cm()
{
    var inches = new ImperialDistance(5);
    var cms = new MetricDistance(MetricDistance.Centimeter.ToMeters() * 12.7);
    var calcCentimeters = Math.Round(inches.ToMetricDistance().ToCentimeters(), 2, MidpointRounding.AwayFromZero);
    var calcInches = Math.Round(cms.ToImperialDistance().ToInches(), 2, MidpointRounding.AwayFromZero);

    Assert.AreEqual(cms.ToCentimeters(), 12.7);
    Assert.AreEqual(calcCentimeters, 12.7);
    Assert.AreEqual(inches.ToInches(), 5);
    Assert.AreEqual(calcInches, 5);
}

您还可以添加扩展方法：

public static MetricDistance Centimeters(this Int32 that)
{
    return new MetricDistance(MetricDistance.Centimeter.ToMeters() * that);
}

[TestMethod]
public void _100cm_plus_300cm_equals_400cm()
{
    Assert.AreEqual(100.Centimeters() + 300.Centimeters(), 400.Centimeters());
}

您可以使用这个简单的策略来测量重量、温度、液体测量等。

Answer 3

.NET Framework 没有这样的东西，但 F# 有 测量单位。

Answer 4

不，框架中没有内置此类单位转换。不过，您自己实施应该很容易。

Answer 5

Csunits 是一个很好的 C# 测量单位库，请参阅 https://github.com/cureos/csunits 。它目前适用于放射治疗，但您可以轻松添加自己的单位和数量。

Answer 6

不，你需要自己制作一个，如下所示：

public class Length
{
    private const double MillimetersPerInch = 25.4;
    private double _Millimeters;

    public static Length FromMillimeters(double mm)
    {
         return new Length { _Millimeters = mm };
    }

    public static Length FromInch(double inch)
    {
         return new Length { _Millimeters = inch * MillimetersPerInch };
    }

    public double Inch { get { return _Millimeters / MillimetersPerInch; } } 
    public double Millimeters { get { return _Millimeters; } }
}

Answer 7

几年后，有很多 Nuget 包可以处理这个问题。其中之一是 https://github.com/angularsen/UnitsNet 它能够处理您想要的内容想。

Length distance = Length.FromInch(15);
distance.Millimeters/ 60;

它还支持很多其他东西。