发送异步电子邮件

Question

我试图使用下面的代码异步发送批量电子邮件。代码运行良好，可以发送电子邮件，但发送时未显示“发送电子邮件...”消息，并且btnCancel也不可见。有谁知道为什么??

Public Sub SendAsyncMail()
    Dim mail As New MailMessage()

    mail.From = New MailAddress("...")
    mail.[To].Add(New MailAddress("..."))
    mail.[To].Add(New MailAddress("..."))
    mail.Subject = "Testing Email"
    mail.Body = "..."

    smtpClient.Credentials = New System.Net.NetworkCredential("...", "...")
    smtpClient.Port = 587
    smtpClient.Host = "smtp.gmail.com"
    smtpClient.EnableSsl = True

    Dim state As [Object] = mail

    AddHandler smtpClient.SendCompleted, AddressOf smtpClient_SendCompleted

    Try
        smtpClient.SendAsync(mail, state)
        lblMsg.Text = "Sending email..."
        btnCancel.Visible = True
    Catch ex As Exception
        lblMsg.Text = ex.Message
    End Try

Answer 1

按钮未显示的事实是一个没有实际意义的事实。除非你把它留在某种延迟的队列中，否则他们无法取消发送该电子邮件。