FieldConverter ConverterKind.Date"dd/MM/yyyy"异常

Question

我尝试读取csv文件.我的第五个记录是一个日期:03/11/2008

这是我的一段代码:

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

我的代码崩溃了:

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

并且有以下例外:行:1.列:41.字段:datum_5.错误将'03/11/2008'转换为类型:'DateTime'.使用格式:'dd/MM/yyyy'

当我这样做:

[FieldConverter(typeof(ConvertDate))]

        public DateTime datum_5;

有了这个:

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");

       }
   }

我得到了这个例外:无法约定03/11/2008 Parameternaam:from

我究竟做错了什么？

Answer 1

它失败的原因是/在自定义日期格式字符串中是文化特定的DateSeparator,如MSDN中所述.

您正在null为IFormatProvider参数指定,因此它使用当前文化,该文化可能具有除/之外的日期分隔符.

最佳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"/"以使其被视为文字斜杠而不是DateSeparator也将起作用(下面的第一个版本).

// 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);