GridView添加ImageButton后邮件无法发送，求适配代码方案

我原本有一段可发送包含GridView表格内容邮件的代码，运行正常。但在GridView最后一列添加ImageButton后，邮件无法发送。我尝试了一段格式化GridView的代码但无效，需要修改原代码，使其支持发送包含或不包含该图片按钮列的邮件。

原发送邮件代码 #

Protected Sub SendRequestMail()
    Dim tryCount As Integer = 5
    Dim failed As Boolean = False
    Do
        Try
            failed = False

            Dim ToMailIDs As String
            ToMailIDs = LblRecipients.Text

            Using sw As New StringWriter()
                Using hw As New HtmlTextWriter(sw)

                    GridView1.RenderControl(hw)
                    Dim sr As New StringReader(sw.ToString())

                    Dim smtpSection As SmtpSection = CType(ConfigurationManager.GetSection("system.net/mailSettings/smtp"), SmtpSection)
                    Dim mm As MailMessage = New MailMessage()

                    mm.From = New MailAddress(smtpSection.From, "Notification")
                    For i As Integer = 0 To ToMailIDs.Split(","c).Length - 1
                        mm.To.Add(New MailAddress(ToMailIDs.Split(","c)(i)))
                    Next

                    mm.ReplyTo = New MailAddress("xxxxx@xxxxx.xxx")

                    mm.Subject = LblMrNumFull.Text & " | " & LblMrDate1x.Text & " | " & LblStorsName1.Text & " - Approval"

                    mm.Body = LblMrNumFull.Text & " | " & LblMrDate1x.Text & " | " & LblStorsName1.Text
                  
                    mm.Body += sw.ToString()

                    mm.Body += "<br />"
                    mm.Body += "Thanking you" 
                    
                    mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure
                    mm.DeliveryNotificationOptions = DeliveryNotificationOptions.Delay
                    mm.Headers.Add("Disposition-Notification-To", "yyyyyy@xxxxx.xxx")

                    ' ----- webconfig mail start
                    mm.IsBodyHtml = True
                    Dim smtp As SmtpClient = New SmtpClient
                    smtp.Host = smtpSection.Network.Host
                    smtp.EnableSsl = smtpSection.Network.EnableSsl
                    Dim networkCred As NetworkCredential = New NetworkCredential(smtpSection.Network.UserName, smtpSection.Network.Password)
                    smtp.UseDefaultCredentials = smtpSection.Network.DefaultCredentials
                    smtp.Credentials = networkCred
                    smtp.Port = smtpSection.Network.Port
                    smtp.Send(mm)
                    ' ----- webconfig mail end

                End Using
            End Using

        Catch ex As Exception
            failed = True
            tryCount = tryCount - 1
        Finally
            Response.Redirect("~/abc/xyx.aspx?NewID=" & Request.QueryString("NewID"))
        End Try

    Loop While failed AndAlso tryCount > 0
End Sub

问题原因 #

当GridView包含服务器控件（如ImageButton）时，直接调用RenderControl会触发控件的视图状态、事件绑定等相关逻辑，容易抛出异常导致邮件发送中断。你之前尝试的代码仅处理了GridView样式，未解决控件渲染的核心问题。

方案1：隐藏ImageButton列后发送邮件 #

如果不需要在邮件中显示按钮，可临时隐藏该列，渲染完成后恢复列的可见性：

Protected Sub SendRequestMail()
    Dim tryCount As Integer = 5
    Dim failed As Boolean = False
    ' 记录最后一列的原始可见状态
    Dim originalColumnVisible As Boolean = GridView1.Columns(GridView1.Columns.Count - 1).Visible

    Do
        Try
            failed = False
            Dim ToMailIDs As String = LblRecipients.Text

            ' 临时隐藏包含ImageButton的最后一列
            GridView1.Columns(GridView1.Columns.Count - 1).Visible = False

            Using sw As New StringWriter()
                Using hw As New HtmlTextWriter(sw)
                    GridView1.RenderControl(hw)
                    Dim gridHtml As String = sw.ToString()

                    Dim smtpSection As SmtpSection = CType(ConfigurationManager.GetSection("system.net/mailSettings/smtp"), SmtpSection)
                    Dim mm As MailMessage = New MailMessage()

                    mm.From = New MailAddress(smtpSection.From, "Notification")
                    ' 优化收件人处理，跳过空值
                    For Each mailId As String In ToMailIDs.Split(","c)
                        If Not String.IsNullOrEmpty(mailId.Trim()) Then
                            mm.To.Add(New MailAddress(mailId.Trim()))
                        End If
                    Next

                    mm.ReplyTo = New MailAddress("xxxxx@xxxxx.xxx")
                    mm.Subject = $"{LblMrNumFull.Text} | {LblMrDate1x.Text} | {LblStorsName1.Text} - Approval"
                    mm.Body = $"{LblMrNumFull.Text} | {LblMrDate1x.Text} | {LblStorsName1.Text}<br/>"
                    mm.Body += gridHtml
                    mm.Body += "<br/>Thanking you"

                    ' 合并通知选项，避免覆盖
                    mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure Or DeliveryNotificationOptions.Delay
                    mm.Headers.Add("Disposition-Notification-To", "yyyyyy@xxxxx.xxx")

                    mm.IsBodyHtml = True
                    Using smtp As New SmtpClient
                        smtp.Host = smtpSection.Network.Host
                        smtp.EnableSsl = smtpSection.Network.EnableSsl
                        Dim networkCred As New NetworkCredential(smtpSection.Network.UserName, smtpSection.Network.Password)
                        smtp.UseDefaultCredentials = smtpSection.Network.DefaultCredentials
                        smtp.Credentials = networkCred
                        smtp.Port = smtpSection.Network.Port
                        smtp.Send(mm)
                    End Using
                End Using
            End Using

        Catch ex As Exception
            failed = True
            tryCount -= 1
        Finally
            ' 恢复列的原始可见状态
            GridView1.Columns(GridView1.Columns.Count - 1).Visible = originalColumnVisible
            Response.Redirect($"~/abc/xyx.aspx?NewID={Request.QueryString("NewID")}")
        End Try

    Loop While failed AndAlso tryCount > 0
End Sub

方案2：保留按钮视觉效果（转为静态HTML图片） #

如果需要在邮件中显示按钮的样子（无法点击），可将服务器端ImageButton替换为静态HTML图片标签：

Protected Sub SendRequestMail()
    Dim tryCount As Integer = 5
    Dim failed As Boolean = False

    Do
        Try
            failed = False
            Dim ToMailIDs As String = LblRecipients.Text

            ' 将所有行的ImageButton替换为静态HTML图片
            For Each row As GridViewRow In GridView1.Rows
                If row.RowType = DataControlRowType.DataRow Then
                    Dim imgBtn As ImageButton = CType(row.Cells(GridView1.Columns.Count - 1).Controls(0), ImageButton)
                    ' 清空控件并添加纯HTML图片
                    row.Cells(GridView1.Columns.Count - 1).Controls.Clear()
                    row.Cells(GridView1.Columns.Count - 1).Text = $"<img src='{imgBtn.ImageUrl}' alt='{imgBtn.AlternateText}' style='border:none;' />"
                End If
            Next

            Using sw As New StringWriter()
                Using hw As New HtmlTextWriter(sw)
                    GridView1.RenderControl(hw)
                    Dim gridHtml As String = sw.ToString()

                    Dim smtpSection As SmtpSection = CType(ConfigurationManager.GetSection("system.net/mailSettings/smtp"), SmtpSection)
                    Dim mm As MailMessage = New MailMessage()

                    mm.From = New MailAddress(smtpSection.From, "Notification")
                    For Each mailId As String In ToMailIDs.Split(","c)
                        If Not String.IsNullOrEmpty(mailId.Trim()) Then
                            mm.To.Add(New MailAddress(mailId.Trim()))
                        End If
                    Next

                    mm.ReplyTo = New MailAddress("xxxxx@xxxxx.xxx")
                    mm.Subject = $"{LblMrNumFull.Text} | {LblMrDate1x.Text} | {LblStorsName1.Text} - Approval"
                    mm.Body = $"{LblMrNumFull.Text} | {LblMrDate1x.Text} | {LblStorsName1.Text}<br/>"
                    mm.Body += gridHtml
                    mm.Body += "<br/>Thanking you"

                    mm.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure Or DeliveryNotificationOptions.Delay
                    mm.Headers.Add("Disposition-Notification-To", "yyyyyy@xxxxx.xxx")

                    mm.IsBodyHtml = True
                    Using smtp As New SmtpClient
                        smtp.Host = smtpSection.Network.Host
                        smtp.EnableSsl = smtpSection.Network.EnableSsl
                        Dim networkCred As New NetworkCredential(smtpSection.Network.UserName, smtpSection.Network.Password)
                        smtp.UseDefaultCredentials = smtpSection.Network.DefaultCredentials
                        smtp.Credentials = networkCred
                        smtp.Port = smtpSection.Network.Port
                        smtp.Send(mm)
                    End Using
                End Using
            End Using

        Catch ex As Exception
            failed = True
            tryCount -= 1
        Finally
            Response.Redirect($"~/abc/xyx.aspx?NewID={Request.QueryString("NewID")}")
        End Try

    Loop While failed AndAlso tryCount > 0
End Sub

内容的提问来源于stack exchange，提问作者samsmuthu