Fill dropdown with parent child relationship data

<removed id="form1" runat="server">




private void FillDropdown()
{
DataTable data = new DataTable("data");

try
{
data = GetDataItem();

DataSet ds = new DataSet();

ds.Tables.Add(data.Copy());

ds.Relations.Add("rsParentChild", ds.Tables[0].Columns["id"],
ds.Tables[0].Columns["ParentId"], false);


foreach (DataRow dr in ds.Tables[0].Rows)
{
if (int.Parse(dr["ParentId"].ToString()) == 0)
{
DropDownList1.Items.Add(new ListItem(dr["Name"].ToString(), dr["Id"].ToString()));

ListItem lstRoot = new ListItem(dr["Name"].ToString(), dr["Id"].ToString());
PopulateTree(dr, lstRoot);
}

}

}
catch (Exception ex)
{

}
}

private void PopulateTree(DataRow dr, ListItem lstRoot)
{
foreach (DataRow row in dr.GetChildRows("rsParentChild"))
{
ListItem lstChild = new ListItem(new String('-', (Int16.Parse(row["HierarchyLevel"].ToString()) - 1)*2) + row["Name"].ToString(), row["Id"].ToString());
DropDownList1.Items.Add(lstChild);
PopulateTree(row, lstChild);
}
}