How to filter records in a form by code using extensions in d365 F&O x++

 In this case I'm filtering vendor invoice journals by creating an extension class in the form datasource -> init() method

I'm trying to filter vendor invoices with USD currency code

[ExtensionOf(formDataSourceStr(vendinvoicejournal, VendInvoiceJour))]

final class RKFormDS_VendInvoiceJournal_Extension

{

    public void init()

    {

        next init();

        str formName =  this.formRun().name();

        str callerName =  this.formRun().args().callerName();

        if(formName == 'VendInvoiceJournal' && callerName == 'RKVendInvoiceJournal')

        {

                          this.query().dataSourceName(this.name()).addRange(fieldnum(VendInvoiceJour, Currency)).value(SysQuery::valueLike("USD"));

            }

        }

    }

For more details please refer following link: http://dynamics-ax-live.blogspot.com/2010/03/how-to-filter-records-in-form-by-code.html