Lookup on form control Dynamics 365 FO on customized form

[Control("String")]

class MCORevisionReasonCodeId

{

    public void lookup()

    {

        Query                   query = new Query();

        QueryBuildDataSource queryBuildDataSource;

        SysTableLookup  sysTableLookup = sysTableLookup::newParameters(tableNum(MCOPORevReasonCodeTable), this);

        queryBuildDataSource = query.addDataSource(tableNum(MCOPORevReasonCodeTable));

        sysTableLookup.addLookupfield(fieldNum(MCOPORevReasonCodeTable, ReasonCodeId),true);

        sysTableLookup.addLookupfield(fieldNum(MCOPORevReasonCodeTable, Description));

        sysTableLookup.parmQuery(query);

        sysTableLookup.performFormLookup();

    }

    public boolean validate()

    {

        boolean ret;

        ret = super();

        if(ret && !MCOPORevReasonCodeTable::find(this.valueStr()))

        {

            ret = checkFailed(strFmt("@SCM:TableFieldValidation", this.valueStr(), "@MCO:RevReasonCode", "@MCO:PORevReasonCode"));

        }

        return ret;

    }

}