即使列表为空，C#列表计数也始终返回1 [英] C# list count always returns 1 even when list is empty

问题描述

我正在尝试调试C#中的方法，但是这里似乎缺少基本的语法技能！该方法接受日期列表作为逗号分隔的文本字符串.该字符串将转换为列表，然后进行处理.但是，似乎即使将一个空字符串传递给该方法，当对列表进行计数时，它仍然会输出1.

I'm trying to debug a method in C# but my basic syntax skills here seem to be lacking! The method accepts a list of dates as a comma-separated text string. This string is converted to a list, then processed. However, it seems that even when an empty string is passed to the method, it still outputs 1 when the list is counted.

代码如下:

public static int DaysLeft(DateTime endDate, DateTime startDate, Boolean excludeWeekends, String excludeDates)
    {
        int counter = 0;

        List<string> excludeDatesList = new List<string>(excludeDates.Split(','));

        counter = excludeDatesList.Count;

        return counter;
    }

如果我将一个空字符串作为excludeDates参数传入，则返回1.如果传递单个日期，则返回1.如果传递两个日期，则返回2等等.在我希望它返回0但实际上返回1的情况下.

If I pass an empty string in as the excludeDates parameter, it returns 1. If I pass a single date it returns 1. If I pass two dates, it returns 2 etc. So it's kind of working except where there's nothing passed in, when I'd expect it to return 0 but it actually returns 1.

有人能指出我正确的方向吗?

Can anyone point me in the right direction?

谢谢

推荐答案

即使是空字符串， Split 也会在数组中返回该字符串，因此列表将用一个空字符串创建，产生的 .Count 为1.[编辑:您可以调用 excludeDates.Split('，'，StringSplitOption.RemoveEmptyEntries)，这样就不会.]

Even for an empty string, Split will return that string in the array, so the list will be created with... one empty string, producing a .Count of 1. [Edit: You can call excludeDates.Split(',', StringSplitOption.RemoveEmptyEntries) so that it doesn't.]

要使您的函数按预期运行，您应该尝试解析从 Split()返回的每个日期"字符串，并仅对有效日期递增计数器.

To make your function behave as you expect, you should probably try to parse each "date" string returned from Split(), and only increment the counter for valid dates.

类似这样的东西:

    int counter = 0;
    var possibleDates = excludeDates.Split(',');

    foreach (var dateStr in possibleDates)
    {
        // Right now it just counts "good" dates, though could also do something
        //  with each date as well
        DateTime dt;
        if (DateTime.TryParse(dateStr, out dt))
            counter++;
    }

    return counter;

如果您正在寻找最简单的方式，则应该只检查参数以查看其是否为空字符串，并在这种情况下返回0:

If you're looking for the simplest way, you should just check the parameter to see if it's the empty string, and return 0 in that case:

if (string.IsNullOrEmpty(excludeDates))
    return 0;

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