DOTNET Interview Question

Export Div Content to Image

Design Page Code:
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript" src="http://cdn.rawgit.com/niklasvh/html2canvas/master/dist/html2canvas.min.js"></script>
<script type="text/javascript">
    function ConvertToImage(btnExport) {
        html2canvas($("#dvTable")[0]).then(function (canvas) {
            var base64 = canvas.toDataURL();
            $("[id*=hfImageData]").val(base64);
            __doPostBack(btnExport.name, "");
        });
        return false;
    }
</script>

</head>
<body>
    <form id="form1" runat="server">

<div id="dvTable" style = "width:340px;background-color:White;padding:5px">
   fggfdgdfgdfgdfg dgdfgfdg dfg df gg<br />
   fggfdgdfgdfgdfg dgdfgfdg dfg df gg<br />
   fggfdgdfgdfgdfg dgdfgfdg dfg df gg<br />
   fggfdgdfgdfgdfg dgdfgfdg dfg df gg<br />
   fggfdgdfgdfgdfg dgdfgfdg dfg df gg<br />
   fggfdgdfgdfgdfg dgdfgfdg dfg df gg<br />
   fggfdgdfgdfgdfg dgdfgfdg dfg df gg<br />
</div>
<br />
<asp:HiddenField ID="hfImageData" runat="server" />
<asp:Button ID="btnExport" Text="Export to Image" runat="server" UseSubmitBehavior="false"
    OnClick="ExportToImage" OnClientClick="return ConvertToImage(this)" />

    </form>
</body>
</html>
Program Page Code:
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void ExportToImage(object sender, EventArgs e)
    {
        string base64 = Request.Form[hfImageData.UniqueID].Split(',')[1];
        byte[] bytes = Convert.FromBase64String(base64);
        Response.Clear();
        Response.ContentType = "image/png";
        Response.AddHeader("Content-Disposition", "attachment; filename=HTML.png");
        Response.Buffer = true;
        Response.Cache.SetCacheability(HttpCacheability.NoCache);
        Response.BinaryWrite(bytes);
        Response.End();
    }

}

Pages

Export Div Content to Image