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Single Click Button with Streaming File

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Brian Goldman
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Brian Goldman asked on 17 May 2011, 10:35 PM
Is it possible to stream a file when using the single click of rad button.
For example I've setup a button exactly like the one in the Single Click Button demo but the button never gets enabled after the file is downloaded. I think it is because I'm using response.clear and response.end methods but I'm not sure. Here is the main part of the code in the button. Is there a workaround to this problem. The button is setup correctly because if I remove this code, it works properly.

Dim downloadBytes As Byte() = pdfConverter.GetPdfFromUrlBytes(URL)
 
       Dim response As System.Web.HttpResponse = System.Web.HttpContext.Current.Response
       response.Clear()
       response.AddHeader("Content-Type", "binary/octet-stream")
       response.AddHeader("Content-Disposition", "attachment; filename=" + FileName + "; size=" + downloadBytes.Length.ToString())
       response.Flush()
       response.BinaryWrite(downloadBytes)
       response.Flush()
       response.End()

Thank you,
Brian

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Pero
Telerik team
answered on 19 May 2011, 08:44 AM
Hi Brian,

The button is not re-enabled because the response is cleared, and then modified to download a file. With a bit of JavaScript you could re-enable the button, after the user is prompted to download the file. I am using the approach described on the following page: http://geekswithblogs.net/GruffCode/archive/2010/10/28/detecting-the-file-download-dialog-in-the-browser.aspx.
Here is an example:
ASPX
<%@ Register TagPrefix="telerik" Namespace="Telerik.Web.UI" Assembly="Telerik.Web.UI" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <script type="text/javascript">
        var fileDownloadCheckTimer;
        function OnClientClicked(sender, args)
        {
            var $ = $telerik.$;
 
            var token = new Date().getTime();
            $('#download_token_value_id').val(token);
 
            //disable button
            sender.set_enabled(false);
 
            fileDownloadCheckTimer = window.setInterval(function ()
            {
                //get cookie and compare
                var cookieValue = readCookie("fileDownloadToken");
                if (cookieValue == token)
                {
                    finishDownload();
                }
            }, 1000);
        }
        function finishDownload()
        {
            window.clearInterval(fileDownloadCheckTimer);
            //clear cookie
            eraseCookie("fileDownloadToken");
            //enable button
            $find("RadButton1").set_enabled(true);
        }
 
        function createCookie(name, value, days)
        {
            if (days)
            {
                var date = new Date();
                date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
                var expires = "; expires=" + date.toGMTString();
            }
            else var expires = "";
            document.cookie = name + "=" + value + expires + "; path=/";
        }
 
        function readCookie(name)
        {
            var nameEQ = name + "=";
            var ca = document.cookie.split(';');
            for (var i = 0; i < ca.length; i++)
            {
                var c = ca[i];
                while (c.charAt(0) == ' ') c = c.substring(1, c.length);
                if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length, c.length);
            }
            return null;
        }
 
        function eraseCookie(name)
        {
            createCookie(name, "", -1);
        }
    </script>
    <div>
        <asp:HiddenField ID="download_token_value_id" runat="server" />
        <telerik:RadButton ID="RadButton1" runat="server" Text="RadButton" OnClick="RadButton1_Click"
            UseSubmitBehavior="false" OnClientClicked="OnClientClicked">
        </telerik:RadButton>
    </div>
    </form>
</body>
</html>

CS
using System;
using System.Web;
 
public partial class Default_Button : System.Web.UI.Page
{
    protected void RadButton1_Click(object sender, EventArgs e)
    {      
        int TestArraySize = 30;
        // create a dummy byte array
        byte[] bytearrayMessageContent = new byte[TestArraySize];
        for (int i = 0; i < TestArraySize; i++)
        {
            // fill character A-J into the dummy array
            bytearrayMessageContent[i] = (byte)(i % 10 + 65);
        }
 
        HttpResponse response = Response;
        response.Clear();
        response.AppendCookie(new HttpCookie("fileDownloadToken", download_token_value_id.Value));
        response.AddHeader("Content-Type", "binary/octet-stream");
        response.AddHeader("Content-Disposition", "attachment; filename=" + "FIle.txt" + "; size=" + TestArraySize.ToString());
        response.BinaryWrite(bytearrayMessageContent);
        response.Flush();
    }
}

I hope this helps.

All the best,
Pero
the Telerik team

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Adam
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commented on 06 Oct 2021, 09:14 AM

For those looking for the original blog post mentioned above:

https://web.archive.org/web/20101109010149/http://geekswithblogs.net/GruffCode/archive/2010/10/28/detecting-the-file-download-dialog-in-the-browser.aspx

Vessy
Telerik team
commented on 06 Oct 2021, 01:57 PM

Thank you for sharing that, Adam!
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Brian Goldman
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answered on 19 May 2011, 11:41 PM
Worked Like a charm. Thank you.
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Brian Goldman
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