Getting Error when using response.write() - asp.net

Question

I need to save a file as .csv in client machine. I am using the code below.
protected void btnGen_Click(object sender, EventArgs e)
{
try
{
string fileName = "test";
string attachment = "attachment; filename=" + fileName + ".csv";
List<string> lst1 = new List<string> { "wert", "fds", "hjgfh", "hgfhg" };
List<string> lst2 = new List<string> { "hgfds", "hdfg", "yretg", "treter" };
List<string> lst3 = new List<string> { "hgfdgf", "gfdg", "gfdgf", "ghfdg" };
List<List<string>> lst = new List<List<string>> { lst1, lst2, lst3 };
StringBuilder sb = new ExportFacade().GenerateStringBuilder(lst);
Response.ContentType = "text/csv" ;
lblProgress.ForeColor = System.Drawing.Color.Green;
lblProgress.Text = "File created and write successfully!";
HttpContext.Current.Response.AddHeader("content-disposition", attachment);
Response.Write(sb.ToString());
lblProgress.ForeColor = System.Drawing.Color.Green;
lblProgress.Text = "File created and write successfully!";
Response.Flush();
Response.End();
}
catch (Exception ex)
{
lblProgress.ForeColor = System.Drawing.Color.Red;
lblProgress.Text = "File Saving Failed!";
}
}
I am not using update panels.
When I click on the button I get the following error
Sys.WebForms.PageRequestManagerParserErrorException: The message
received from the server could not be parsed. Common causes for this
error are when the response is modified by calls to Response.Write(),
response filters, HttpModules, or server trace is enabled.
It will be a great help to me if you can help me to get rid of this problem.
thank you.

Answer 1

I solved it. Ajax script manager in the master page has created the problem. After removing it, the function worked properly. But labels are not being updated as response is not for the page.