Pretty String Manipulation - regex

Question

I have the following string which I wish to extract parts from:
<FONT COLOR="GREEN">201 KAR 2:340.</FONT>
In this particular case, I wish to extract the numbers 201,2, and 340, which I will later use to concatenate to form another string:
http://www.lrc.state.ky.us/kar/201/002/340reg.htm
I have a solution, but it is not easily readable, and it seems rather clunky. It involves using the mid function. Here it is:
intTitle = CInt(Mid(strFontTag,
InStr(strFontTag, ">") + 1,
(InStr(strFontTag, "KAR") - InStr(strFontTag, ">"))
- 3))
I would like to know if perhaps there is a better way to approach this task. I realize I could make some descriptive variable names, like intPosOfEndOfOpeningFontTag to describe what the first InStr function does, but it still feels clunky to me.
Should I be using some sort of split function, or regex, or some more elegant way that I have not come across yet? I have been manipulating strings in this fashion for years, and I just feel there must be a better way. Thanks.

Answer 1

<FONT[^>]*>[^\d]*(\d+)[^\d]*(\d+):(\d+)[^\d]*</FONT>

Answer 2

The class
Imports System
Imports System.IO
Imports System.Text
Imports System.Text.RegularExpressions
Imports System.Xml
Imports System.Xml.Linq
Imports System.Linq
Public Class clsTester
'methods
Public Sub New()
End Sub
Public Function GetTitleUsingRegEx(ByVal fpath$) As XElement
'use this function if your input string is not a well-formed
Dim result As New XElement(<result/>)
Try
Dim q = Regex.Matches(File.ReadAllText(fpath), Me.titPattern1, RegexOptions.None)
For Each mt As Match In q
Dim t As New XElement(<title/>)
t.Add(New XAttribute("name", mt.Groups("name").Value))
t.Add(New XAttribute("num1", mt.Groups("id_1").Value))
t.Add(New XAttribute("num2", mt.Groups("id_2").Value))
t.Add(New XAttribute("num3", mt.Groups("id_3").Value))
t.Add(mt.Value)
result.Add(t)
Next mt
Return result
Catch ex As Exception
result.Add(<error><%= ex.ToString %></error>)
Return result
End Try
End Function
Public Function GetTitleUsingXDocument(ByVal fpath$) As XElement
'use this function if your input string is well-formed
Dim result As New XElement(<result/>)
Try
Dim q = XElement.Load(fpath).Descendants().Where(Function(c) Regex.IsMatch(c.Name.LocalName, "(?is)^font$")).Where(Function(c) Regex.IsMatch(c.Value, Me.titPattern2, RegexOptions.None))
For Each nd As XElement In q
Dim s = Regex.Match(nd.Value, Me.titPattern2, RegexOptions.None)
Dim t As New XElement(<title/>)
t.Add(New XAttribute("name", s.Groups("name").Value))
t.Add(New XAttribute("num1", s.Groups("id_1").Value))
t.Add(New XAttribute("num2", s.Groups("id_2").Value))
t.Add(New XAttribute("num3", s.Groups("id_3").Value))
t.Add(nd.Value)
result.Add(t)
Next nd
Return result
Catch ex As Exception
result.Add(<error><%= ex.ToString %></error>)
Return result
End Try
End Function
'fields
Private titPattern1$ = "(?is)(?<=<font[^<>]*>)(?<id_1>\d+)\s+(?<name>[a-z]+)\s+(?<id_2>\d+):(?<id_3>\d+)(?=\.?</font>)"
Private titPattern2$ = "(?is)^(?<id_1>\d+)\s+(?<name>[a-z]+)\s+(?<id_2>\d+):(?<id_3>\d+)\.?$"
End Class
The usage
Sub Main()
Dim y = New clsTester().GetTitleUsingRegEx("C:\test.htm")
If y.<error>.Count = 0 Then
Console.WriteLine(String.Format("Result from GetTitleUsingRegEx:{0}{1}", vbCrLf, y.ToString))
Else
Console.WriteLine(y...<error>.First().Value)
End If
Console.WriteLine("")
Dim z = New clsTester().GetTitleUsingXDocument("C:\test.htm")
If z.<error>.Count = 0 Then
Console.WriteLine(String.Format("Result from GetTitleUsingXDocument:{0}{1}", vbCrLf, z.ToString))
Else
Console.WriteLine(z...<error>.First().Value)
End If
Console.ReadLine()
End Sub
Hope this helps.

Answer 3

regex pattern: <FONT[^>]*>.*?(\d+).*?(\d+).*?(\d+).*?<\/FONT>

Answer 4

I think #Jean-François Corbett has it right.
Hide it away in a function and never look back
Change your code to this:
intTitle = GetCodesFromColorTag("<FONT COLOR="GREEN">201 KAR 2:340.</FONT>")
Create a new function:
Public Function GetCodesFromColorTag(FontTag as String) as Integer
Return CInt(Mid(FontTag, InStr(FontTag, ">") + 1,
(InStr(FontTag, "KAR") - InStr(FontTag, ">"))
- 3))
End Function