how to add field to listpage (make it sortable and filterable) not a field in datasources in it.

1. Create a view (CITCustTransView )
2. Add to the form as new datasource ( Outer join) to the data source which it can be linked.
3. Add link to view and existing data source through code.


[Extensionof(formDataSourceStr(CustopenTrans,CITCustTransView ))]
final class CITCustOpenTrans_Extension
{
    public void init()
    {
        QueryBuildDataSource  queryDataSourceLink;
        next init();
        queryDataSourceLink  = this.query().datasourcetable(tablenum(CITCustTransView));
        queryDataSourceLink.addlink(fieldNum(CustTrans,Invoice),fieldnum(CITCustTransView,InvoiceId));
        queryDataSourceLink.addlink(fieldNum(CustTrans,TransDate),fieldnum(CITCustTransView,InvoiceDate));
        queryDataSourceLink.addlink(fieldNum(CustTrans,Voucher),fieldnum(CITCustTransView,LedgerVoucher));
        queryDataSourceLink.addlink(fieldNum(CustTrans,AccountNum),fieldnum(CITCustTransView,InvoiceAccount));

    }

}