Match “THIS” And Replace with “THAT” RegEx Vb.Net

Question

Trying to find out how to find and replace text with corresponding values.

For Example

1) fedex to FedEx 2) nasa to NASA 3) po box to PO BOX

Public Function FindReplace(ByVal s As String) As String

    Dim MatchEval As New MatchEvaluator(AddressOf RegexReplace)

    Dim Pattern As String = "(?<f1>fedex|nasa|po box)"

    Return Regex.Replace(s, Pattern, MatchEval, RegexOptions.IgnoreCase)

End Function

Public Function RegexReplace(ByVal m As Match) As String
    Select Case LCase(m.Groups("f1").Value)
        Case "fedex"
            Return "FedEx"
        Case "nasa"
            Return "NASA"
        Case "po box"
            Return "PO BOX"
    End Select
End Function

The above code is working fine for fixed values but don't know how to use the above code to match added values on run-time like db to Db.

Answer 1

I'd guess, that the only thing here you need Regex for is IgnoreCase option. If so, then I would like to suggest not to use Regex at all. Use String functionality instead:

Dim input As String = "fEDeX"
Dim pattern As String = "fedex"
Dim replacement As String = "FedEx"

Dim result As String

result = input.ToLowerInvariant().Replace(pattern, replacement)

But if you still need Regex, then this should work:

result = Regex.Replace(input, pattern, replacement, RegexOptions.IgnoreCase)

Example:

Sub Main()
  Dim replacements As New Dictionary(Of String, String)()
  replacements.Add("fedex", "FedEx")
  replacements.Add("nasa", "NASA")
  replacements.Add("po box", "PO BOX")

  Dim result As String = Replace("fedex, nAsA, po box, etc", replacements)
End Sub

Private Function Replace(ByVal input As String, ByVal replacements As Dictionary(Of String, String)) As String
  For Each item In replacements
    input = Regex.Replace(input, item.Key, item.Value, RegexOptions.IgnoreCase)
  Next

  Return input
End Function

Answer 2

Found the solution by using List and did the performance test against dictionary object suggested by Anton Kedrov both methods takes almost same time to complete but i don't know the dictionary method will be good or not for longer replacement list because it loop through all the list to find the match entry for replacement.

I thank you all for your suggestion and advice.

Sub Main()
    Dim lst As New List(Of String)

    lst.Add("NASA")
    lst.Add("FedEx")
    lst.Add("PO BOX")

    MsgBox(FindReplace("this is testing fedex naSa PO box"))
End Sub

Public Function FindReplace(ByVal s As String) As String
    Dim Pattern As String = "(?<f1>fedex|nasa|po box)"
    Dim MatchEval As New MatchEvaluator(AddressOf RegexReplace)
    Return Regex.Replace(s, Pattern, MatchEval, RegexOptions.IgnoreCase)

End Function

Public Function RegexReplace(ByVal m As Match) As String
    Dim Found As String
    Found = lst.Find(Function(value As String) LCase(value) = LCase(m.Groups("f1").Value))
    Return Found
End Function