使用 isDate 返回 true vb.net
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Using isDate return true vb.net
提问by Gimo Gilmore
When I'm using isDate()Method in .NET. It returns invalid result. Why "AD05AD09" is read as date. following is the code i'm using. Please give me proper reason for this
当我isDate()在 .NET 中使用Method 时。它返回无效的结果。为什么将“AD05AD09”读作日期。以下是我正在使用的代码。请给我适当的理由
Dim value As String
value = "AD05AD09"
If IsDate(value) Then
Dim oDate As Date
oDate = CDate(value)
MsgBox(Format(oDate, "yyyy-MM-dd"))
Else
MsgBox("a")
End If
回答by loadingnow
It is counted as a date because the first "AD" like said in http://en.wikipedia.org/wiki/Anno_Domini, AD is placed before the year, but because the 05 is not 4 digit but 2 digit, the functions treat it as the month. The second AD counts as a valid delimiter in the date like in "12AD12AD2008" is 12/12/2008.
它被算作日期，因为第一个“AD”就像http://en.wikipedia.org/wiki/Anno_Domini 中所说的那样，AD 放在年份之前，但是因为 05 不是 4 位而是 2 位，所以函数把它当作月份。第二个 AD 算作日期中的有效分隔符，例如“12AD12AD2008”是 12/12/2008。
So,
所以，
CDate("AD05AD09") '= 05/09
CDate("10AD10AD2000") '=10/10/2000
and so on.
等等。
But BC doesn't work, because BC can't be stored in a date, since you can't store negative years...
但是 BC 不起作用，因为 BC 不能存储在日期中，因为您不能存储负年份...
回答by ilans
As writtern in MSDN:
正如MSDN 中所写：
IsDate returns True if Expression is of the Date Data Type or can be converted to Date; otherwise, it returns False.
如果表达式是日期数据类型或可以转换为日期，则 IsDate 返回 True；否则，它返回 False。
But you should go for the common ways, which are DateTime.Parse, DateTime.ParseExact, Convert.ToDateTimeand more.
但是你应该去为常见的方式，这是DateTime.Parse，DateTime.ParseExact，Convert.ToDateTime和更多。
See this MSDNexample:
请参阅此MSDN示例：
Dim dateValue As Date
Dim dateString As String = "2/16/2008"
Try
dateValue = Date.Parse(dateString)
Console.WriteLine("'{0}' converted to {1}.", dateString, dateValue)
Catch e As FormatException
Console.WriteLine("Unable to convert '{0}'.", dateString)
End Try
