并非所有代码路径都返回一个值 - 枚举练习

Question

我试图执行一个简单的代码只是为了研究枚举主题.然而,我遇到了这个问题:"并非所有代码路径都返回一个值".这是代码:

namespace ConsoleAppTest
{
    class Program
    {
        enum Seasons { Winter, Spring, Summer, Fall };

        static void Main(string[] args)
        {
            WhichSeason(3);
        }

        static Seasons WhichSeason(int month)
        {
            if (month >= 1 || month <= 3)
            {
                return Seasons.Winter;
            }
            else if (month >= 4 || month <= 6)
            {
                return Seasons.Spring;
            }
            else if (month >= 7 || month <= 9)
            {
                return Seasons.Summer;
            }
            else if (month >= 10 || month <= 12)
            {
                return Seasons.Fall;
            }
        }
    }
}

我想知道什么可能导致这个问题.谢谢 :)

Answer 1

你应该处理这个else案子.你的month整数也可以是<1或>12.

static Seasons WhichSeason(int month)
{
    if (month >= 1 && month <= 3)
    {
        return Seasons.Winter;
    }
    else if (month >= 4 && month <= 6)
    {
        return Seasons.Spring;
    }
    else if (month >= 7 && month <= 9)
    {
        return Seasons.Summer;
    }
    else if (month >= 10 && month <= 12)
    {
        return Seasons.Fall;
    }
    else
    {
        throw new ArgumentOutOfRangeException("invalid month");
    }
}

所以,如果你打电话

WhichSeason(13); //throws exception