如何将“ dd / mm / yyyy”日期显示为“ yyyy-mm-dd”日期

Question

I keep seeing similar questions for Python and PHP, but I don't have access to those functions since I'm not using either of them. The language I'm using is VB.NET. So if I have:

Dim date1 = "06/19/2015"

then I want to convert it to

"2015-06-19"

I can replace to "/" character using Replace() really easily, but I can't figure out how to order the day, month, and year around without it being too complex. Again, lots of similar questions on the web, but I'm having trouble finding one on that isn't using Python and PHP.

Answer 1

Build up a list of possible formats and use DateTime.TryParseExact() . Then pass your desired output format to DateTime.ToString() .

    Dim date1 As String = "06/19/2015"
    Dim allowedFormats() As String = {"M/d/yy", "M/dd/yy", "MM/d/yy", "MM/dd/yy", "M/d/yyyy", "M/dd/yyyy", "MM/d/yyyy", "MM/dd/yyyy"}
    Dim dt As DateTime
    If DateTime.TryParseExact(date1, allowedFormats, Globalization.CultureInfo.InvariantCulture, Globalization.DateTimeStyles.None, dt) Then
        Dim date2 As String = dt.ToString("yyyy-MM-dd")
        Debug.Print(date1 & " --> " & date2)
    End If