我可以使用关键字 "in" 以某种方式分隔方法声明中的参数吗？

Question

我想创建一个使用关键字in而不是逗号来分隔方法声明中的参数的方法;类似于foreach(a in b)方法。

例

类结构

public class Length
{
    public double Inches;
    public double Feet;
    public double Yards;
    public enum Unit { Inch, Foot, Yard }
    Dictionary<Unit, double> inchFactor = new Dictionary<Unit, double>()
    {
        { Unit.Inch, 1 },
        { Unit.Foot, 12 },
        { Unit.Yard, 36 }
    };
    public Length(double value, Unit unit)
    {
        this.Inches = value * inchFactor[unit];
        this.Feet = this.Inches / inchFactor[Unit.Foot];
        this.Yards = this.Inches / inchFactor[Unit.Yard];
    }
}

类中的方法定义

// I'd like to know how to use "in" like this  ↓
public List<Length> MultiplesOf(Length divisor in Length dividend)
{
    double inchEnumeration = divisor.Inches;
    List<Length> multiples = new List<Length>();
    while (inchEnumeration <= dividend.Inches)
    {
        multiples.Add(new Length(inchEnumeration, Length.Unit.Inch));
        inchEnumeration += divisor.Inches;
    }
    return multiples;
}

理想的实施

private void DrawRuler()
{
    Length eighthInch = new Length(0.125, Length.Unit.Inch);
    Length oneFoot = new Length(1, Length.Unit.Foot);
    // Awesome.
    List<Length> tickGroup = Length.MultiplesOf(eighthInch in oneFoot);
    double inchPixels = 10;
    foreach (Length tick in tickGroup)
    {
        // Draw ruler.
    }
}

<小时 />

我已经考虑过创建新关键字，但看起来 C# 不支持定义关键字。

Answer 1

如注释中所述，您无法在 C# 中定义自定义关键字（除非您扩展编译器，这是一项高级任务）。但是，如果您的目标是澄清这两个参数的含义，那么我建议您改用命名参数：

// Define the method as usual:
public List<Length> MultiplesOf(Length divisor, Length dividend)
{
    // ...
}
// Then call it like so, explicitly showing what is the divisor and the dividend:  
List<Length> tickGroup = Length.MultiplesOf(divisor: eighthInch, dividend: oneFoot);

Answer 2

虽然您无法重新定义现有关键字，但还有其他方法可以使用Fluent Interface以略有不同的方式完成任务：

public class Length
{
    // ...
    public static IFluentSyntaxProvider MultiplesOf(Length divisor)
    {
        return new FluentSyntaxProvider(divisor);
    }
    public interface IFluentSyntaxProvider
    {
        List<Length> In(Length dividend);
    }
    private class FluentSyntaxProvider : IFluentSyntaxProvider
    {
        private Length divisor;
        public FluentSyntaxProvider(Length divisor)
        {
            this.divisor = divisor;
        }
        public List<Length> In(Length dividend)
        {
            double inchEnumeration = divisor.Inches;
            List<Length> multiples = new List<Length>();
            while (inchEnumeration <= dividend.Inches)
            {
                multiples.Add(new Length(inchEnumeration, Length.Unit.Inch));
                inchEnumeration += divisor.Inches;
            }
            return multiples;
        }
    }
}

使用示例 ：

// Awesome.
List<Length> tickGroup = Length.MultiplesOf(eighthInch).In(oneFoot);