how can i get the value from .aspx.cs to .cs page

.aspx.cs(webinterface)
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Collections;
using System.Configuration;
using System.Text;
namespace WebInterface.UI.aPMG
{
public partial class Overalldshbrd : BasePage
{
// BusinessLogicLayer.DA da = new BusinessLogicLayer.DA();

protected void Page_Load(object sender, EventArgs e)
{

if (!Page.IsPostBack)
{
BusinessLogicLayer.Overalldshbrd Overalldshbd = new BusinessLogicLayer.Overalldshbrd();
string graph = Overalldshbd.ovraltask();
string graph1 = Overalldshbd.Ageing();
string graph2 = Overalldshbd.Ageingiss();
string graph3 = Overalldshbd.kpiweek();
txtPrjID.Text = this.PrjID.ToString();-----here am getting prjid number ho ...