public void FilllListStudent()
    {
        int id      = int.Parse(Request.QueryString["Id"].ToString());
        var student = (from j in km.StudentsInActivities
                       join ee in km.Students on j.StudentId equals ee.IdentityNumber
                       where j.ActiviteId == id
                       select new
        {
            ee.Name,
            j.StudentId,
            j.ActiviteId

            //Name = (from d in km.Students where d.IdentityNumber == j.StudentId select d.Name).FirstOrDefault()
        }).ToList();


        LstStudent.DataSource = student;
        LstStudent.DataBind();
    }
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            if (Request.QueryString["Id"] != null)
            {
                FilllListStudent();
                int activeid = int.Parse(Request.QueryString["Id"].ToString());

                var ta = (from k in km.StudentActivities
                          where k.Id == activeid
                          select k).FirstOrDefault();

                txtFrom.Text      = MyDate.getDate(ta.DateFrom.ToString());
                txtTo.Text        = MyDate.getDate(ta.DateTo.ToString());
                txtActivity.Text  = ta.Activity;
                txtFieldName.Text = ta.FieldName;
                txtSeat.Text      = ta.Seat;
            }
            LstStudent.DataBind();
        }
    }