Urgent plz help! Storing new record in a new row of a datatable using Session.

I have Desktop.aspx page with Gridview1 and Detailsview1 controls. My requirement is, if I click on a button in Detailsview1, that particular product name and it's price should be stored in a datatable which is bound to GridView2. So far, I am successful in accomplishing this. However, if I click on another product , a new row is inserted in Datatable, but it shows the first added record and not the recent one. I have stored datatable object in session. My source code is as follows:

public partial class Desktops : System.Web.UI.Page

{

protected void Page_Load(object sender,EventArgs e)

{

if (!Page.IsPostBack)

{

DataTable mydt = new DataTable();

DataRow myrow;

mydt.Columns.Add("Product Name");

mydt.Columns.Add("Price");

Session["MyDataTable"] = mydt;

}

protected voidDetailsView1_ItemCommand(object sender,DetailsViewCommandEventArgs e) {

if (e.CommandName == "save")

{

ArrayList FavD = (ArrayList)Session["FavDesktops"];

if (FavD == null)

{

FavD = new ArrayList();

}

FavD.Add(DetailsView1.Rows[2].Cells[1].Text);

FavD.Add(DetailsView1.Rows[7].Cells[1].Text);

Session["FavDesktops"] = FavD;

DataTable t = (DataTable)Session["MyDataTable"];

DataRow myrow = t.NewRow();

myrow = t.NewRow();

myrow["Product Name"] = FavD[0].ToString();

myrow["Price"] = FavD[1].ToString();

t.Rows.Add(myrow);

t.AcceptChanges();

Session["MyDataTable"] = t;

GridView2.DataSource = t;

GridView2.DataBind();

}

protected void Page_PreRender(objectsender, EventArge)

{

string sFavsHTML = "

You are considering the following desktops:

ArrayList alFavorites = (ArrayList)Session["FavDesktops"];

if (alFavorites != null)

{

foreach (string sItem inalFavorites)

{

sFavsHTML += sItem +"
";

}

else

{

sFavsHTML += "None";

}

sFavsHTML += "

lblconsidering.Text = sFavsHTML;

}