从excel读取时，以字符串格式比较两个日期 [英] compare two dates in string format while reading from excel

问题描述

我在excel字段中有两个日期字段。我想比较这两个领域。但由于excel字段的值是字符串转换为DateTime可能会导致问题。那么有什么方法可以比较它们吗？我认为这是不可能的，即使它不会100％安全失败。它的预感并不多。请告诉我是否有办法

Hi,

I have two date fields in excel field. I want to compare these two fields. But since the value of excel fields is string convert them into DateTime may cause problem. So is there any way to compare them? I think its not possible, even if it is it won't be 100 % fail safe. Its my hunch nothing much. Please let me know if there is a way

推荐答案

不，这不可能，而且肯定不是安全 - 你真的想转换它们首先是一个DateTime值，然后进行比较。



如果日期是ISO格式，那么可以进行字符串比较：yyyy-MM-dd

因为字符串比较在第一个差异处停止，并使用字符比较来确定顺序。但是......如果一个日期是2014-01-3而另一个是2014-01-14，那么字符串比较就会得到错误的顺序。



你可以手动处理字符串并对各个部分进行比较 - 但是你正在复制将它转换为DateTime的工作！ ：笑：

No, it's not really possible, and it certainly isn't "safe" - you really do want to convert them to a DateTime value first and then do the comparison.

It's all ok to do a string compare if the dates are in ISO format: yyyy-MM-dd
Because string comparisons stop at the first difference and use character comparisons to determine order. But...if one date is 2014-01-3 and the other is 2014-01-14 then a string comparison gets them in the wrong order.

You could manually process the string and do the comparison on the various parts - but then you are duplicating the work that converting it to a DateTime does anyway! :laugh:

如果您要比较的字段有数据格式。

您可以确定该字段将采用日期时间格式。



有关字段/行/列的数据格式的更多信息：格式化 - 在Excel中的日期 [ ^ ]



然后你可以做DateTime.Parse（你的字段）。



如果你有两个DateTime结构实例，你可以使用运算符== ，！=和>，<，> =，< =分别在后来，更早，不早，不迟的意义上。此外，您可以使用减法运算符（ - ），它以System.TimeSpan的形式返回结果。这是一套全面的操作员，可以满足您的所有比较需求。

If you have Data format on the fields you want to compare.
You can know for sure the field will be in a datetime format.

for more info on data format of fields/rows/columns: format-a-date in excel[^]

then you could do DateTime.Parse(your field).

When you have two instances of DateTime structure you can use operators "==", "!=" and ">", "<", ">=", "<=" in the sense "later", "earlier", "not earlier", "not later", respectively. Also, you can use subtraction operator ("-") which returns the result in the form of System.TimeSpan. This is a comprehensive set of operators to cover all your comparison needs.

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