ajax nothing written to the database

im trying to send data from sidenav located in my default.aspx page to another page called addstudy.aspx . im getting the alert that the study was inserted in the database , but in fact nothing is inserted , instead , in my console im getting , 500 internal server error , any help please? my code is below

Default.aspx ( on button click)

<script type="text/javascript">







       function insert() {

           var xmlhttp = new XMLHttpRequest();
           var anchors = document.getElementById('mySidenav').getElementsByTagName('a');

           for (var i = 0; i < anchors.length; i++) {


               alert(anchors[i].text);
               alert(anchors[i].href);


           xmlhttp.open("GET", "addnewstudy.aspx?nm=" + anchors[i].text + "&gd=" + anchors[i].href + "&opr=insert", false);
           xmlhttp.send(null);

           alert("New Study inserted in database");

       }

            }


</script>

then in my addnewstudy.aspx

  SqlConnection conn = new SqlConnection("Data Source=.\\SQLEXPRESS;Initial Catalog=LLDB;Integrated Security=True;Pooling=False");

    string name;
    string gender;
    string opr;

    protected void Page_Load(object sender, EventArgs e)
    {
        opr = Request.QueryString["opr"].ToString();

        if (opr == "insert")
        {
            name = Request.QueryString["nm"].ToString();
            gender = Request.QueryString["gd"].ToString();


            SqlCommand cmd = conn.CreateCommand();
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = "insert into tbl_myresearches (NodeName,NodeLink) values('" + name.ToString() + "','" + gender.ToString() + "')";
            cmd.ExecuteNonQuery();
            cmd.Dispose();
            conn.Close();

        }
    }