Coding to Send Email on a Button Click With and Without attachment

 
Private Sub sendbutton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles sendbutton.Click
        If con.State = ConnectionState.Open Then
            con.Close()
        End If
        Try
            Dim mail, atchmail As New MailMessage
            mail.Subject = subjecttextbox.Text
            mail.To.Add(totextbox.Text)
            mail.From = New MailAddress(usernametextbox.Text)
            mail.Body = bodytextbox.Text
            If attachmenttextbox.Text <> "" Then 'If attachment is there than this code will be executed
                Dim attachment As System.Net.Mail.Attachment
                attachment = New System.Net.Mail.Attachment(attachmenttextbox.Text)
                mail.Attachments.Add(attachment)

                Dim smtp As New SmtpClient("smtp.gmail.com")
                smtp.EnableSsl = True
                smtp.Credentials = New System.Net.NetworkCredential(usernametextbox.Text, passwordtextbox.Text)
                smtp.Port = "587"
                smtp.Send(mail)
            Else 'If there is no attachment than this code is executed
                Dim smtp As New SmtpClient("smtp.gmail.com")
                smtp.EnableSsl = True
                smtp.Credentials = New System.Net.NetworkCredential(usernametextbox.Text, passwordtextbox.Text)
                smtp.Port = "587"
                smtp.Send(mail)
            End If

            MsgBox("Message Sent Successfully", MsgBoxStyle.Information)
            totextbox.Clear()
            subjecttextbox.Clear()
            bodytextbox.Clear()
            attachmenttextbox.Clear()
            usernametextbox.Text = "sample_email@gmail.com"
            passwordtextbox.Clear()
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
        

    End Sub