extract part of string

Question

Hello experts,

I'm reading Vcf contact files, the only fields I have issues reading are 2 multi-line fields: NOTE and KEY

Because I don't know how many lines it lasts, the fields order can be different in each file so just need an idea how to parse these 2 multi-line fields?

By the way, how to parse this REV string to date and time?

20240623T081758Z

TryParseExact does not parse strings like "20221114T225355Z" or if it does not end of Z :(

Sample:

BEGIN:VCARD
VERSION:VERSION:2.1
N;LANGUAGE=en-us:;Georges
FN:Georges
NOTE;ENCODING=QUOTED-PRINTABLE:       <=
body>  Saturday, September 17, 2022 7:34 PM:  Notes are here
  
 Notes are here
 =
 
   
ORG:comp co;dept
KEY;X509;ENCODING=BASE64:
 MIIF6DCCA9CgAwIBAgIQSn+Q+fs4+1BweWY3kIcBwDANBgkqhkiG9w0BAQsFADCBgTELMAkGA1UE
 BhMCSVQgdfhjhgktyryiuyoiuohmhgcGGDFHGJKJUKKHJGJHGJHGJHGJGHBQaWV0cm8xFzAVBgNV
 bw8mToZYbb1dFGHHFGHGFHGFHGFHJGF9dfNtkzg==
REV:20240623T081758Z
END:VCARD

Thanks in advance.

Answer

DateTime.ParseExact works here, you just need to use the right custom flags.

Dim input As String = "20240623T081758Z"

Dim dt As DateTime = DateTime.ParseExact(value, "yyyyMMddTHHmmssZ", System.Globalization.CultureInfo.CurrentCulture, System.Globalization.DateTimeStyles.AdjustToUniversal)

A few notes here. Assuming your hours are in 24-hour format. Using current culture for typical defaults. Because you're getting the time in UTC with the Z, DateTime doesn't tend to like that. If you always know it is that then you can simply strip it off. But specifying AdjustToUniversal seems to handle this case as well. If you cannot do that then just strip off the Z before parsing.

Answer

Hi @StewartBW ,

You can use a state machine approach to properly detect and parse the fields, even if they span multiple lines.

        Dim inNote As Boolean = False
        Dim inKey As Boolean = False

        For Each line As String In lines
            If line.StartsWith("NOTE") Then
                inKey = False
                inNote = True
                noteBuilder.Append(line.Substring(line.IndexOf(":"c) + 1).Trim())
            ElseIf line.StartsWith("KEY") Then
                inNote = False
                inKey = True
                keyBuilder.Append(line.Substring(line.IndexOf(":"c) + 1).Trim())
            ElseIf line.StartsWith("END:VCARD") Then
                inNote = False
                inKey = False
            ElseIf line.StartsWith("BEGIN:VCARD") Then
                inNote = False
                inKey = False
            ElseIf line.StartsWith("VERSION:") Then
                inNote = False
                inKey = False
            ElseIf line.StartsWith("N;LANGUAGE") Then
                inNote = False
                inKey = False
            ElseIf line.StartsWith("FN:") Then
                inNote = False
                inKey = False
            ElseIf line.StartsWith("ORG:") Then
                inNote = False
                inKey = False
            ElseIf line.StartsWith("REV:") Then
                inNote = False
                inKey = False
            Else
                If inNote Then
                    noteBuilder.Append(line.Trim())
                End If
                If inKey Then
                    keyBuilder.Append(line.Trim())
                End If
            End If
        Next

Uses DateTime.TryParseExact to parse the REV string using the exact format provided.

        Dim revString As String = "20240623T081758Z"
        Dim revDate As DateTime

        If DateTime.TryParseExact(revString, "yyyyMMdd'T'HHmmss'Z'", 
                                  CultureInfo.InvariantCulture, 
                                  DateTimeStyles.AssumeUniversal, 
                                  revDate) Then
            Console.WriteLine("Parsed Date: " & revDate.ToString("yyyy-MM-dd HH:mm:ss"))
        Else
            Console.WriteLine("Failed to parse date.")
        End If

Best Regards.

Jiachen Li

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extract part of string

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