VB.NET如何发布打开的文件？

Imports System.IO
Imports System.Net.Mail

Module Module1
    Sub Main()
        Dim filePath As String = "C:\example.txt"
        Dim attachmentPath As String = "C:\attachment.txt"

        Using fs As FileStream = File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.Read)
            Dim mail As New MailMessage()
            mail.From = New MailAddress("sender@example.com")
            mail.To.Add("recipient@example.com")
            mail.Subject = "Subject"
            mail.Body = "Body"

            Dim attachment As New Attachment(attachmentPath, MediaTypeNames.Application.Octet)
            mail.Attachments.Add(attachment)

            Dim smtp As New SmtpClient("smtp.example.com")
            smtp.Credentials = New NetworkCredential("username", "password")
            smtp.Send(mail)
        End Using
    End Sub
End Module