Error message when download file from gridview asp.net c#

protected void Button3_Click(object sender, EventArgs e)
    {
        
        Button bn = sender as Button;
        GridViewRow gr = bn.NamingContainer as GridViewRow;
        string path = GridView1.DataKeys[gr.RowIndex].Value.ToString();
        Response.ContentType = "image/jpg";
        Response.AddHeader("Content-Disposition", "attachment;filename=\"" + path + "\"");
        Response.TransmitFile(Server.MapPath(path)); // The error is here
        Response.End();
        
 
        
    }

 protected void Button1_Click(object sender, EventArgs e)
    {
      
            string filename2 = Path.GetFileName(FileUpload1.PostedFile.FileName);
            FileUpload1.SaveAs(Server.MapPath("Files/" + filename2));
            SqlCommand com = new SqlCommand("insert into song (sname,path) values (@s,@p)", c1.cn);
            com.Parameters.AddWithValue("@s", SqlDbType.NVarChar).Value = TextBox1.Text;
            com.Parameters.AddWithValue("@p", SqlDbType.NVarChar).Value = "Files/" + filename2;
            c1.cn.Open();
            com.ExecuteNonQuery();
            c1.cn.Close();
           
        
    }