asp.net form submitted twice
<p>I have a web page with a form and a submit button, and in the server side I used a session value to prevent the form submit twice, which is like the initial value of the session is 0 and turn it to 1 after user click submit button, every time submit button will check the session value first. </p>

<p>But, when our project published, I found there were two records for the same person (which means they submit twice I guess, and it didn't happen very often maybe on one or two persons), and the time interval between these two records is very small, like 0.3 second, so first I thought they might double click the submit button, but after I tried on my computer, it still only insert one record into the database</p>

<p>I am confused how does this happen, and how to prevent it?</p>

<p>Here is the code:</p>

<pre><code>        protected void Page_Init(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            Session["IsBackForwordPayment"] = 0;
        }
    }

    protected void submit_Click(object sender, EventArgs e)
    {

       if (Session["IsBackForwordPayment"] != null &amp;&amp; Session["IsBackForwordPayment"].ToString() != "0")
            Response.Redirect("~/pages/renewal/duplicaterenewal.aspx");

.......
}
</code></pre>

<p>Is it possible because that after checking the session value the program just redirect to another page but not terminate the submit process ??</p>
