c# - 用任何设计模式或更好的方法替换 if else 语句

Question

这段代码看起来不干净而且这个 if 条件可以增长

public int VisitMonth(int months)
    {
        int visit = 0;

        if (months <= 1)
        {
            visit = 1;
        }
        else if (months <= 2)
        {
            visit = 2;
        }
        else if (months <= 4)
        {
            visit = 3;
        }
        else if (months <= 6)
        {
            visit = 4;
        }
        else if (months <= 9)
        {
            visit = 5;
        }
        else if (months <= 12)
        {
            visit = 6;
        }
        else if (months <= 15)
        {
            visit = 7;
        }
        else if (months <= 18)
        {
            visit = 8;
        }
        else if (months <= 24)
        {
            visit = 9;
        }
        else if (months <= 30)
        {
            visit = 10;
        }
        else if (months <= 36)
        {
            visit = 11;
        }
        else if (months <= 48)
        {
            visit = 12;
        }
        else if (months <= 60)
        {
            visit = 13;
        }
        else
        {
            visit = 14;
        }
        return visit;
    }

这个问题有更好的解决办法吗？遗憾的是，该函数不是线性的，因此以数学方式对其进行编码并不容易。

Answer 1

应该更适合重用:你可以像这样用“inRange”方法写一个“Interval”类:

 public struct Interval<T>
       where T : IComparable
{
    public T Start { get; set; }
    public T End { get; set; }
    public T Visit { get; set; }

    public Interval(T visit, T start, T end)
    {
        Visit = visit;
        Start = start;
        End = end;
    }

    public bool InRange(T value)
    {
      return ((!Start.HasValue || value.CompareTo(Start.Value) > 0) &&
          (!End.HasValue || End.Value.CompareTo(value) >= 0));
    }
}

然后像这样使用:

public static readonly List<Interval<int>> range = new List<Interval<int>>
        {
                new Interval<int>(1, 0, 1),
                new Interval<int>(2, 1, 2),
                new Interval<int>(3, 2, 4),
                new Interval<int>(4, 4, 6),
                new Interval<int>(5, 6, 9),
                new Interval<int>(6, 9, 12),
                new Interval<int>(7, 12, 15),
                new Interval<int>(8, 15, 18),
                new Interval<int>(9, 18, 24),
                new Interval<int>(10, 24, 30),
                new Interval<int>(11, 30, 36),
                new Interval<int>(12, 36, 48),
                new Interval<int>(13, 48, 60),
                new Interval<int>(14, 60, int.MaxValue)
        };

var months = 5;
var visit = range.Where(x => x.InRange(months)).Select(x => x.Visit).FirstOrDefault();