Cum中的枚举和IEnumerable

Question

我的TIME Enum包含年度,每月,每周,每日和每小时.

在这里,我想确定哪个是最小值,并希望返回.

我怎样才能做到这一点 ？这是我试过的代码.

private Time DecideMinTime(IEnumerable<Time> g)
{
    var minTime = Time.Hourly;
    foreach (var element in g)
    {
        minTime = element;
    }
    return minTime;
}   

Answer 1

假设枚举元素的数值决定了最小值:

private Time DecideMinTime(IEnumerable<Time> g)
{
    if (g == null) { throw new ArgumentNullException("g"); }

    return (Time)g.Cast<int>().Min();
}

如果数值表示相反的顺序,那么您将使用.Max()而不是.Min().

如图所示,数字顺序不一致.这可以通过使用指示正确顺序的映射来解决:

static class TimeOrdering
{
    private static readonly Dictionary<Time, int> timeOrderingMap;

    static TimeOrdering()
    {
        timeOrderingMap = new Dictionary<Time, int>();

        timeOrderingMap[Time.Hourly] = 1;
        timeOrderingMap[Time.Daily] = 2;
        timeOrderingMap[Time.Weekly] = 3;
        timeOrderingMap[Time.Monthly] = 4;
        timeOrderingMap[Time.Annual] = 5;
    }

    public Time DecideMinTime(IEnumerable<Time> g)
    {
        if (g == null) { throw new ArgumentNullException("g"); }

        return g.MinBy(i => timeOrderingMap[i]);
    }

    public TSource MinBy<TSource, int>(
        this IEnumerable<TSource> self,
        Func<TSource, int> ordering)
    {
        if (self == null) { throw new ArgumentNullException("self"); }
        if (ordering == null) { throw new ArgumentNullException("ordering"); }

        using (var e = self.GetEnumerator()) {
            if (!e.MoveNext()) {
                throw new ArgumentException("Sequence is empty.", "self");
            }

            var minElement = e.Current;
            var minOrder = ordering(minElement);

            while (e.MoveNext()) {
                var curOrder = ordering(e.Current);

                if (curOrder < minOrder) {
                    minOrder = curOrder;
                    minElement = e.Current;
                }
            }

            return minElement;
        }
    }
}