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Editorial Team
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Asked: 2026-06-10T11:08:48+00:00

I got the following code protected override void Render(HtmlTextWriter writer) { // Write the

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I got the following code

protected override void Render(HtmlTextWriter writer) 
{

    // Write the HTML into this string builder

    StringBuilder sb = new StringBuilder();
    StringWriter sw = new StringWriter(sb);
    HtmlTextWriter hWriter = new HtmlTextWriter(sw);
    base.Render(hWriter);

    string pageHTML = sb.ToString(); 

    // Write it back to the server
    writer.Write(pageHTML);
    if (Convert.ToBoolean(this.ViewState["SendEmail"])) 
    {
        string HTML = "";
        HTML = "<!DOCTYPE HTML PUBLIC '-//IETF//DTD HTML//EN'>";
        HTML += "<html>";
        HTML += "<head>";
        HTML += "<meta http-equiv='Content-Type'";
        HTML += "content='text/html; charset=iso-8859-1'>";
        HTML += "<title>Order Information</title>";
        HTML += "</head>";
        HTML += "<body>";
        HTML += "See attachment for information.";
        HTML += "</body>";
        HTML += "</html>";

        MailMessage mail = new MailMessage("from@xxx.com", "to@xxx.com", "Subject", HTML);
        mail.IsBodyHtml = true;

        string path = @"d:\websites\plate.html";

        using (StreamWriter sw11 = File.CreateText(path))
        {
            sw11.WriteLine(pageHTML);
        }

        mail.Attachments.Add(new Attachment(path));

        SmtpClient client = new SmtpClient("192.168.1.127");

        client.Send( mail );

        Response.Write("<script>alert('Your information has been sent.')</script>");

        this.ViewState["SendEmail"] = false;
    }

}

After a fresh clean/build of my solution, when I press the send button, this function is called and the html page is sent in attachment by mail without a problem. But if I try to press again the send button, I’m getting “System.IO.IOException: The process cannot access the file ‘d:\websites\plate.html’ because it is being used by another process.” The error occur when I’m trying to open the file. What’s wrong?

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1 Answer

  1. Editorial Team

    As Eric has pointed out, you should have the SmtpClient in a using statement – ditto MailMessage.

    However, you’d still end up writing to the file system for no obvious reason. I’d strongly advise you to use one of the Attachment constructors which doesn’t require a file to start with. You can write to a MemoryStream, rewind it, and then provide that to the Attachment for example.

    Aside from anything else, that would mean you wouldn’t have a problem if multiple threads (or processes) tried running this code at the same time.

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