Problem with Datagrid

Question

hi friends, i have got a small problem I want to add a new row to the Datagrid(not bound to nay database table) when i select any value from a dropdownlist(which is in one of the columns of the datagrid) such that the previous rows should maintain their value as before and only a new row is added. i am pasting the code chunk below please tell me what is going wrong because the row gwets added only once and no event is fired second time private void Page_Load(object sender, System.EventArgs e) { if(!Page.IsPostBack) { Table1 = new Table(); TableRow row = new TableRow(); Table1.Rows.Add (row); DataGrid1.DataSource=Table1.Rows; DataGrid1.DataBind(); } } protected void dd1_SelectedIndexChanged(object sender, EventArgs e) { DataGridItem dgi = (DataGridItem)(((Control)sender).NamingContainer); DropDownList ddl = (DropDownList) dgi.Cells[0].Controls[1]; DataGrid dg =(DataGrid) dgi.Parent.Parent; TableCell tc = new TableCell(); Label l1 = new Label(); l1.Text ="hi"; tc.Controls.Add(l1); DataGridItem dgItem = new DataGridItem(dgi.ItemIndex+1,0,ListItemType.Item); dgItem.Cells.Add(tc); DataGrid1.Controls[0].Controls.AddAt(dgi.ItemIndex+1,dgItem); }