FieldConverter ConverterKind.Date“dd / MM / yyyy”例外 [英] FieldConverter ConverterKind.Date "dd/MM/yyyy" exception

问题描述

我尝试读取csv文件。
我的第五条记录包含日期：03/11/2008

I try to read a csv file. my fifth record contans a date: 03/11/2008

这是我的一段代码：

    [FieldConverter(ConverterKind.Date, "dd/MM/yyyy")]
    public DateTime datum_5;

我的代码在此崩溃：

Result[] results= (Result[])engine.ReadFile(@"..\Data\expo.txt");

并且有以下异常：
行：1.列：41.字段：datum_5。将'03 / 11/2008'转换为type：'DateTime'时出错。使用格式：'dd / MM / yyyy'

And with this exception: Line: 1. Column: 41. Field: datum_5. Error Converting '03/11/2008' to type: 'DateTime'. Using the format: 'dd/MM/yyyy'

当我这样做时：

[FieldConverter(typeof(ConvertDate))]

        public DateTime datum_5;

：

internal class ConvertDate : ConverterBase
   {

       /// <summary>
       /// different forms for date separator : . or / or space
       /// </summary>
       /// <param name="from">the string format of date - first the day</param>
       /// <returns></returns>

       public override object StringToField(string from)
       {
           DateTime dt;

           if (DateTime.TryParseExact(from, "dd.MM.yyyy", null, DateTimeStyles.None, out dt))
               return dt;

           if (DateTime.TryParseExact(from, "dd/MM/yyyy", null, DateTimeStyles.None, out dt))
               return dt;

           if (DateTime.TryParseExact(from, "dd MM yyyy", null, DateTimeStyles.None, out dt))
               return dt;

           throw new ArgumentException("can not make a date from " + from, "from");

       }
   }

make a date from 03/11/2008
Parameternaam：from

I got this exception: can not make a date from 03/11/2008 Parameternaam: from

我做错了什么？

推荐答案

它失败的原因是/在自定义日期格式字符串如MSDN中所述的文化特定的DateSeparator 。

The reason it's failing is that / in a custom date format string is a culture-specific DateSeparator as described in MSDN.

您正在指定 null 为 IFormatProvider 参数，因此它使用当前的文化，可能有除了/.

You are specifying null for the IFormatProvider argument, so it's using the current culture, which presumably has a date separator other than /.

最好的解决方案是明确指定CultureInfo.InvariantCulture（下面的第二个版本）。转义自定义日期格式字符串中的'/'，以便它被当作一个字符斜杠而不是一个DateSeparator也将工作（下面的第一个版本）。

The best solution is to explicitly specify CultureInfo.InvariantCulture (second version below). Escaping the '/' in your custom date format string so that it is treated as a literal slash rather than a DateSeparator will also work (first version below).

// Set current culture to a culture that uses "." as DateSeparator
Thread.CurrentThread.CurrentCulture = new CultureInfo("de-DE");
// This will work - escaping means it uses a literal / as the separator
DateTime.TryParseExact(s, @"dd\/MM\/yyyy", null, DateTimeStyles.None, out result);

// This is better - Culture.InvariantCulture uses / for the DateTimeFormatInfo.DateSeparator
// and you clearly express the intent to use the invariant culture
DateTime.TryParseExact(s, "dd/MM/yyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result);

// This will fail - / means use DateTimeFormatInfo.DateSeparator which is "." in the de-DE culture
DateTime.TryParseExact(s, "dd/MM/yyyy", null, DateTimeStyles.None, out result);

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