即使try块未抛出异常，捕获块仍在执行？

Question

I am trying to send a mail via goDaddy mail server. The mail is being sent (I am receiving it in my mailbox) but the catch block is executing and landing me to the contact page with querystring msg as "fail"

    protected void Page_Load(object sender, EventArgs e)
{
    if (Request.QueryString["username"] != null && Request.QueryString["email"] != null && Request.QueryString["msg"] != null)
    {
        try
        {
            string name = Request.QueryString[0];
            string email = Request.QueryString[1];
            string msg = Request.QueryString[2];
            SmtpClient smtp = new SmtpClient("relay-hosting.secureserver.net", 25);
            //smtp.EnableSsl = false;
            smtp.Send("feedback@solutionpoint98.com", "b.soham1991@gmail.com", "feedback", "Name:" + name + "\n e-mail:" + email + "\n Subject:" + msg);
            Response.Redirect("contact.html?msg=success");
        }
        catch(Exception ex)
        {
            Response.Redirect("contact.html?msg=fail");
        }
    }
    else
    {
        Response.Redirect("contact.html");
    }
}

If the mail is being sent, shouldn't it redirect to "contact.html?msg=success"?

Answer 1

The problem is that your first Response.Redirect() is actually throwing a ThreadAbortException. This is due to the fact that .Redirect internally calls the Response.End method, prematurely ending the Response in this case.

The correct way to do this is to use the overloaded Response.Redirect(string url, bool endResponse), which allows you to suppress the internal call to Response.End by setting endResponse to false ... which will prevent this error from being thrown.

This is all covered in this MS support article: http://support.microsoft.com/kb/312629/EN-US/

Just modify your code to look like this:

protected void Page_Load(object sender, EventArgs e)
{
    if (Request.QueryString["username"] != null && Request.QueryString["email"] != null && Request.QueryString["msg"] != null)
    {
        try
        {
            string name = Request.QueryString[0];
            string email = Request.QueryString[1];
            string msg = Request.QueryString[2];
            SmtpClient smtp = new SmtpClient("relay-hosting.secureserver.net", 25);
            //smtp.EnableSsl = false;
            smtp.Send("feedback@solutionpoint98.com", "b.soham1991@gmail.com", "feedback", "Name:" + name + "\n e-mail:" + email + "\n Subject:" + msg);
            Response.Redirect("contact.html?msg=success", false);
        }
        catch(Exception ex)
        {
            Response.Redirect("contact.html?msg=fail", false);
        }
    }
    else
    {
        Response.Redirect("contact.html", false);
    }
}