C# - Dynamic Adding Rows Into Table?

How can I add rows in a table from server-side?

if (!Page.IsPostBack)
{
Session["table"] = TableId;
}
else
{
TableId = (Table)Session["table"];
}
protected void btnAddinRow_Click(object sender, EventArgs e)
{
num_row = (TableId.Rows).Count;
TableRow r = new TableRow();
TableCell c1 = new TableCell();
TableCell c2 = new TableCell();
TextBox t = new TextBox();
t.ID = "textID" + num_row;
t.EnableViewState = true;
r.ID = "newRow" + num_row;
c1.ID = "newC1" + num_row;
c2.ID = "newC2" + num_row;
c1.Text = "New Cell - " + num_row;
c2.Controls.Add(t);
r.Cells.Add(c1);
r.Cells.Add(c2);
TableId.Rows.Add(r);
Session["table"] = TableId;
}

in debug I found out the number in the "TableID", but the rows are not drawn. Have you got an idea about this issue?