Button Not Firing Event

I have a page containing a datagrid, which works. On that page I have a button which is supposed to trigger a download of the data from the datagrid in Excel format. However, the button isn't firing the event. The C# code-behind I have is:

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using umbraco;
namespace MyDataExport
{
public partial class DataExport : System.Web.UI.UserControl
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
GridView1.DataSource = BindData();
GridView1.DataBind();

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