Why my method call 3 times?

How many times are you using that webpart on the same or other templates on that page load? Also where are you performing your button click events? Can you share some pseudo code?

now i use it as follows in transformation:

<%@ Register Src="~/CMSWebParts/MyWebParts/DownloadButton.ascx" TagName="DownloadControl" TagPrefix="htz" %>

<htz:DownloadControl ID="DownloadControl1" runat="server" EcGuid='<%# Eval("Guid").ToString() %>' WithAuthentication="true" WithCaptcha="true" WithPayment="false" FileCost="1000" />

and my click event :

protected void downloadBtn_Click(object sender, EventArgs e)
{
    EventLogProvider.LogException("00000000000", "CMSWebParts_MyWebParts_DownloadButton", new Exception("ex: "));
    if (WithCaptcha && captchaElem.Visible)
    {
        if (captchaElem.IsValid())
        {
            if (string.IsNullOrEmpty(ItemId))
            {
                CustomTableItem cti = CustomTableItem.New("customtable.Status");
                cti.SetValue("UserIp", HttpContext.Current.Request.UserHostAddress);
                cti.SetValue("UserGuid", MembershipContext.AuthenticatedUser.UserGUID);
                cti.SetValue("UserName", MembershipContext.AuthenticatedUser.UserName);
                cti.Insert();
            }
        }
    }
}

Is this only happening while you view your page in the cmsdesk or on the front end/live site as well?

this is only happening while i view my page in the live site.

my complete code :

protected void downloadBtn_Click(object sender, EventArgs e)
{
    EventLogProvider.LogException("00000000000", "CMSWebParts_MyWebParts_DownloadButton", new Exception("ex: "));
    if (WithCaptcha && captchaElem.Visible)
    {
        if (captchaElem.IsValid())
        {
            if (string.IsNullOrEmpty(ItemId))
            {
                CustomTableItem cti = CustomTableItem.New("customtable.Status");
                cti.SetValue("UserIp", HttpContext.Current.Request.UserHostAddress);
                cti.SetValue("UserGuid", MembershipContext.AuthenticatedUser.UserGUID);
                cti.SetValue("UserName", MembershipContext.AuthenticatedUser.UserName);
                cti.SetValue("UserEmailAddress", MembershipContext.AuthenticatedUser.Email);
                cti.SetValue("PageAlias", HttpContext.Current.Request.RawUrl.Substring(firstIndex, lastIndex - firstIndex));
                cti.SetValue("DownloadCount", 1);
                cti.Insert();
            }
            else
            {
                var existing = CustomTableItemProvider.GetItem(int.Parse(ItemId), "customtable.Status");
                var currentDownloadCount = ValidationHelper.GetInteger(existing.GetValue("DownloadCount", -1), -1);
                if (currentDownloadCount <= MaxDownloadCount)
                {
                    existing.SetValue("DownloadCount", currentDownloadCount + 1);
                    existing.Update();
                }
                else
                {
                    return;
                }
            }

            var documentFile = CustomTableItemProvider.GetItems("customtable.Document")
                .TopN(1)
                .WhereEquals("FileNameGuid", EcGuid);
            if (!DataHelper.DataSourceIsEmpty(documentFile))
            {
                DownloadFile(documentFile.Tables[0].Rows[0]["DocFilePath"].ToString(),
                    documentFile.Tables[0].Rows[0]["FileNameGuid"].ToString() + ".pdf");
            }
        }
        else
        {
            SecurityCodeMessage.Text = "error100";
        }
    }
    else
    {
        if (string.IsNullOrEmpty(ItemId))
        {
            CustomTableItem cti = CustomTableItem.New("customtable.Status");
            cti.SetValue("UserIp", HttpContext.Current.Request.UserHostAddress);
            cti.SetValue("UserGuid", MembershipContext.AuthenticatedUser.UserGUID);
            cti.SetValue("UserName", MembershipContext.AuthenticatedUser.UserName);
            cti.SetValue("UserIsRegister", !MembershipContext.AuthenticatedUser.IsPublic());
            cti.SetValue("PageAlias", HttpContext.Current.Request.RawUrl.Substring(firstIndex, lastIndex - firstIndex));
            cti.SetValue("DownloadCount", 1);
            cti.Insert();
        }
        else
        {
            var existing = CustomTableItemProvider.GetItem(int.Parse(ItemId), "customtable.Status");
            var currentDownloadCount = ValidationHelper.GetInteger(existing.GetValue("DownloadCount", -1), -1);
            if (currentDownloadCount <= MaxDownloadCount)
            {
                existing.SetValue("DownloadCount", currentDownloadCount + 1);
                existing.Update();
            }
            else
            {
                return;
            }
        }

        var documentFile = CustomTableItemProvider.GetItems("customtable.Document")
            .TopN(1)
            .WhereEquals("FileNameGuid", EcGuid);
        if (!DataHelper.DataSourceIsEmpty(documentFile))
        {
            DownloadFile(documentFile.Tables[0].Rows[0]["DocFilePath"].ToString(),
                documentFile.Tables[0].Rows[0]["FileNameGuid"].ToString() + ".pdf");
        }
    }
}

In this section, instead of (+1), 3 times to be added :

existing.SetValue("DownloadCount", currentDownloadCount + 1);

i use from this control in my transformation of repeater Which repeats custom table record

Ok, so you are using this control in a transformation? It would be called for each item in the transformation, so could that be the reason? It is going to run that for each of the items that is loaded in. You may want to put it somewhere else or add a conditonal clause to only do it if it is the first item.

I found problem

When the file download starts, "Internet download manager" has sent several requests to the server that it caused my method called 3 times.

Now, how do I solve this problem?؟

may I ask how you solve this problem?