Generate line numbers in the form + AX 2012

1) In order to generate the line numbers in the form insert the following code in the table insert method:

void insert()
{
LedgerBalColumnsDim lbColumnsDim;
;
if (this.Column == 0)
{
select maxof(Column) from lbColumnsDim
where lbColumnsDim.BalanceSheet == this.BalanceSheet;
this.Column = lbColumnsDim.Column + 1;
}
super();
}
Take the same table instance that is used in the form datasource.