SharePoint 2010 Web Part Gridview to CSV

I have written an web part that has a gridview on it that I populate and display on assorted web part pages.   All that seems to work fine.  Now I need to capture the gridview data and present it to a user on their clicking a "Load CSV" button on that web part.  

The code follows and indeed works:

   private void ExportGridToCSV()
        {            
            Response.Clear();
            Response.Buffer = true;
            Response.AddHeader("content-disposition", "attachment;filename=Employee.csv");
            Response.Charset = "";
            Response.ContentType = "application/text";
            GridEmployee.AllowPaging = false;
            GridEmployee.DataBind();

            StringBuilder columnbind = new StringBuilder();
            for (int k = 0; k < GridEmployee.Columns.Count; k++)
            {

                columnbind.Append(GridEmployee.Columns[k].HeaderText + ',');
            }

            columnbind.Append("\r\n");
            for (int i = 0; i < GridEmployee.Rows.Count; i++)
            {
                for (int k = 0; k < GridEmployee.Columns.Count; k++)
                {

                    columnbind.Append(GridEmployee.Rows[i].Cells[k].Text + ',');
                }

                columnbind.Append("\r\n");
            }
            Response.Output.Write(columnbind.ToString());
            Response.Flush();
            Response.End();

        }

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The problem is that once the click event calls this code, the page no longer seems to be connected to the code behind and subsequent clicks don't get handled (I have a breakpoint which is never reached in the beginning of the click events).