how to send an email with attachment in vb.net?

Here is a great example

Public Sub SendMailOneAttachment(ByVal From As String, _
      ByVal sendTo As String, ByVal Subject As String, _
      ByVal Body As String, _
      Optional ByVal AttachmentFile As String = "", _
      Optional ByVal CC As String = "", _
      Optional ByVal BCC As String = "", _
      Optional ByVal SMTPServer As String = "")

        Dim myMessage As MailMessage

        Try
            myMessage = New MailMessage()
            With myMessage
                .To = sendTo
                .From = From
                .Subject = Subject
                .Body = Body
                .BodyFormat = MailFormat.Text
                'CAN USER MAILFORMAT.HTML if you prefer

                If CC <> "" Then .Cc = CC
                If BCC <> "" Then .Bcc = ""

                If FileExists(AttachmentFile) Then _
                 .Attachments.Add(AttachmentFile)

            End With

            If SMTPServer <> "" Then _
               SmtpMail.SmtpServer = SMTPServer
            SmtpMail.Send(myMessage)

        Catch myexp As Exception
            Throw myexp
        End Try

    End Sub

Public Sub SendMailMultipleAttachments(ByVal From As String,_
    ByVal sendTo As String, ByVal Subject As String, _
    ByVal Body As String, _
    Optional ByVal AttachmentFiles As ArrayList = Nothing, _
    Optional ByVal CC As String = "", _
    Optional ByVal BCC As String = "", _
    Optional ByVal SMTPServer As String = "")

        Dim myMessage As MailMessage
        Dim i, iCnt As Integer

        Try
            myMessage = New MailMessage()
            With myMessage
                .To = sendTo
                .From = From
                .Subject = Subject
                .Body = Body
                .BodyFormat = MailFormat.Text
                'CAN USER MAILFORMAT.HTML if you prefer

                If CC <> "" Then .Cc = CC
                If BCC <> "" Then .Bcc = ""

                If Not AttachmentFiles Is Nothing Then
                    iCnt = AttachmentFiles.Count - 1
                    For i = 0 To iCnt
                        If FileExists(AttachmentFiles(i)) Then _
                          .Attachments.Add(AttachmentFiles(i))
                    Next

                End If

            End With

            If SMTPServer <> "" Then _
              SmtpMail.SmtpServer = SMTPServer
            SmtpMail.Send(myMessage)


        Catch myexp As Exception
            Throw myexp
        End Try
    End Sub

    Private Function FileExists(ByVal FileFullPath As String) _
     As Boolean
        If Trim(FileFullPath) = "" Then Return False

        Dim f As New IO.FileInfo(FileFullPath)
        Return f.Exists

    End Function

See this sample:

http://msdn.microsoft.com/en-us/library/system.net.mail.attachment.aspx

Essentially, you'll need to add something like this:

Dim file as string = "c:\Documents\MyFile.txt"
''// Create  the file attachment for this e-mail message.
Attachment data = new Attachment(file, MediaTypeNames.Application.Octet);
''// Add time stamp information for the file.
ContentDisposition disposition = data.ContentDisposition;
disposition.CreationDate = System.IO.File.GetCreationTime(file);
disposition.ModificationDate = System.IO.File.GetLastWriteTime(file);
disposition.ReadDate = System.IO.File.GetLastAccessTime(file);
''// Add the file attachment to this e-mail message.
message.Attachments.Add(data);