Download file from gridview control using asp.net

Generally this is my code here download properly but no data coming like empty
please check and reply now please

Source code:

public partial class Images : System.Web.UI.Page
{
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["connectionstring"].ConnectionString);
SqlDataAdapter sda;
SqlCommand cmd;
DataSet ds;

protected void Page_Load(object sender, EventArgs e)
{
cmd = new SqlCommand("select * from ImageUpdate where Email=@Email", con);
cmd.Parameters.AddWithValue("@Email", Session["Email"].ToString());
sda = new SqlDataAdapter(cmd);
ds = new DataSet();
sda.Fill(ds, "ImageUpdate");

lblMail.Text = ds.Tables["ImageUpdate"].Rows[0][2].ToString();
imgupd.ImageUrl = ds.Tables["ImageUpdate"].Rows[0][3].ToString();

if (!IsPostBack)
{
grid();
}
}
private void grid()
{
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["connectionstring"].ConnectionString);
string query = "select Name,Photo from ImageUpdate";
SqlDataAdapter da = new SqlDataAdapter(query, con);
DataTable table = new DataTable();
da.Fill(table);
GridView1.DataSource = table;
GridView1.DataBind();

}
protected void GridView1_SelectedIndexChanged(object sender, EventArgs e)
{
con.Open();
cmd = new SqlCommand("select Name,Photo from ImageUpdate where Email=@Email", con);
cmd.Parameters.AddWithValue("@Email", Session["Email"].ToString());
SqlDataReader sdr = cmd.ExecuteReader();
if (sdr.Read())
{
Response.Clear();
Response.Buffer = true;
Response.ContentType = sdr["Photo"].ToString();
Response.AddHeader("content-disposition", "attachment;filename=" + sdr["Name"].ToString());
//Response.Charset = "";
//Response.Cache.SetCacheability(HttpCacheability.NoCache);
//Response.BinaryWrite((byte[])sdr["Mobile"]);
Response.End();
}
}
}

is the default excel file actually retrieve and store in folder of solution explorer

that folder to retrieve and download here default excel or image anything please reply me