If I declare a DataTable dt on PageLoad or before it as Global will the data in it will destroy with every Postback event

public partial class FAS_Reports_Forms_frmRpt_PurchReg : System.Web.UI.Page
{
// DataTable dt  =  new DataTable();
    Common cmn = new Common();
    Cls_Messages objMsg = new Cls_Messages();
    Cls_DateClass objDate = new Cls_DateClass();
    Consts consts = new Consts();
    protected void Page_Load(object sender, EventArgs e)
    {
        //cmn.CheckSession(Session["UName"]);
        if (!IsPostBack)
        {
            try
            {
               // divTitle.Visible = false;
                //if (cmn.chkfinyrdt(consts.localdate) == true)
                //{
                //    txttodt.text = consts.localdate;
                //}
                //else
                //{
                //    txttodt.text = cmn.pubenddt;
                //}
                hdPubYear.Value = Convert.ToString(Session["pubYearCode"]);
                txtFromDt.Text = cmn.pubStartDt;
                hid_unm.Value = Convert.ToString(Session["UName"]);
                Session["MonYr"] = null;
                Session["Report_Name"] = null;
                //Session["Report_Title"] = null;
                Session["dtAttend"] = null;
                string sql = "SELECT party.Id," +
                         "lEFT( party.PartyName +REPLICATE('…', 40), 40)+ ISNULL(CITY.Description,'') TTT " +
                         "FROM Party party " +
                         "Join City on CITY.Id = party.City_Id ORDER BY party.PartyName";
                cmn.fillDDLNormal(ddlAccount, sql, "id", "TTT");
                fillTitle();
            }
            catch (Exception)
            {
                return;
            }
        }
    }