Get only part of file name and delete from server folder in asp.net vb

I’m trying get get only the last part of a file name in a server folder between the “_” and “.pdf” in order to delete specific files only.
The files in the invoices folder are like this: Invoice_12345.pdf, Invoice_2345.pdf, Invoice_5555.pdf, etc. I need to extract the “12345”, “2345”, and “5555”, then I need to delete the file if it is not contained in a database query.

With the following code, I wish to extract the digits from the files in the folder, so how do I get the number between “_” and “.pdf”?

Dim files() As String = Directory.GetFiles(Server.MapPath("/Contents/Invoices/"))
For Each file As String In files            
        list.Add(file)
    
Next

Then I need to delete the file from the server if the extracted number is not contained in a dataset I query from the database, but maybe that is a question for a different post.

For example, for Invoice "5555"
If PaidFull = True 
File.Delete(file)
End If

Of course, I would have to then get the full file name to delete if from the server at that point.

Answers:

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Method 1

This is a way to get only the numbers :

  For Each file As String In files

            Dim the_number As String = Path.GetFileNameWithoutExtension(file)

            the_number = the_number.Substring(the_number.LastIndexOf("_") + 1, the_number.Length - the_number.LastIndexOf("_") - 1)


            list.Add(the_number )

        Next

Or with Regex (ty to Jimi) :

dim the_number = Regex.Match(file, "_(d+).").Groups(1).Value

Method 2

You really don’t need to mess with parsing the file name if you are sure the number won’t pop up somewhere in the directory path.

    'Dim list = Directory.GetFiles("C:SomeDirectory").ToList
    Dim myTestList As New List(Of String) From {"Invoice_12345.pdf", "Invoice_2345.pdf", "Invoice_5555.pdf"}
    For Each fileName In myTestList
        If fileName.Contains("5555") Then
            Debug.Print(fileName) 'Or do what you need to do
        End If
    Next

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