c# - 如何使用 C# ASP.Net 在电子邮件中发送图表控件

Question

我已经编写了下面的代码来使用 C# ASP.Net 在电子邮件正文消息（不是作为附件）中发送 Gridview 和图表图像。

    StringBuilder sb = new StringBuilder();
    string MailSturcture;

    using (System.IO.StringWriter sw = new StringWriter())
    {
        using (HtmlTextWriter hw = new HtmlTextWriter(sw))
        {
            gvDaySummary.RenderControl(hw);
            hw.WriteBreak();
            BarChart1.RenderControl(hw);

            System.IO.StringReader sr = new StringReader(sw.ToString());

            MailMessage mail = new MailMessage();
            mail.From = new MailAddress("noreply@xxx.com", "aura");
            mail.To.Add("abc@xxx.com");

            mail.Subject = "Daily Payment Summary";
            mail.IsBodyHtml = true;
            sb.AppendFormat(sw.ToString());

            MailSturcture = sb.ToString();
            mail.Body = MailSturcture;

            System.Net.Mail.SmtpClient smtp = new SmtpClient();
            smtp.Host = "smtpout.secureserver.net";
            smtp.Port = 80;
            System.Net.NetworkCredential NetworkCred = new System.Net.NetworkCredential();
            NetworkCred.UserName = "abc@xxx.com";
            NetworkCred.Password = "xxx";
            smtp.UseDefaultCredentials = true;
            smtp.Credentials = NetworkCred;
            smtp.EnableSsl = false;
            smtp.Send(mail);
        }
    }

    public override void VerifyRenderingInServerForm(System.Web.UI.Control control)
    {
        /* Verifies that the control is rendered */
    }

如果我删除 BarChart1 控件，那么 Gridview 会完美地显示在邮件消息中，但是当我添加时，BarChart1 会引发以下错误。

Script control 'BarChart1' is not a registered script control. Script controls must be registered using RegisterScriptControl() before calling RegisterScriptDescriptors().
Parameter name: scriptControl

任何人都可以请澄清我到底是什么错误。