assigning Value to drop down list

protected void Page_Load(object sender, EventArgs e)
      {
          if (!Page.IsPostBack)
          {
              Client_Combo();
}
          protected void Client_Combo()
        {
            Client objClient = new Client();
            drpClient.DataSource = objClient.GetGridValues();
            drpClient.DataValueField= "Id";
            drpClient.DataTextField = "Name";        
            drpClient.DataBind();           
        }
the saved value i am retrieving from table and assigning to DataTable  from that i want to assign dropdownlist for that i writen code like below
  BLL.Transaction objTrans = new BLL.Transaction();
            DataTable dtTrans = null;
            dtTrans = objTrans.GetTransactionValues(SelectedID);
            DTO.TransactionInfo TransInfo = new DTO.TransactionInfo();                 
            if (dtTrans.Rows[0]["Client"].ToString() != null)
            {
             drpClient.Items.FindByValue(dtTrans.Rows[0]["Client"].ToString()).Selected = true;
              
            }