Lookup() in Dynamic AX

public void lookup()
{
    Query query = new Query();
    QueryBuildDataSource queryBuildDataSource;
    QueryBuildRange queryBuildRange;
    SysTableLookup sysTableLookup = SysTableLookup::newParameters(tableNum(custTable), this);
    sysTableLookup.addLookupField(fieldNum(CustTable, AccountNum));
    sysTableLookup.addLookupMethod(tablemethodstr(CustTable,Name));
    queryBuildDataSource = query.addDataSource(tableNum(CustTable));
    queryBuildRange = queryBuildDataSource.addRange(fieldNum(CustTable, AccountNum));
    queryBuildRange.value();
    sysTableLookup.parmQuery(query);
    sysTableLookup.performFormLookup();
    //super();
}

/// Another method////

public void lookup()
{
    Query query = new Query();
    QueryBuildDataSource queryBuildDataSource;
    QueryBuildRange queryBuildRange; 
    SysTableLookup sysTableLookup = SysTableLookup::newParameters(tableNum(custTable), this); 
    sysTableLookup.addLookupField(fieldNum(CustTable, AccountNum));
    sysTableLookup.addLookupField(fieldNum(CustTable, CustGroup)); 
    queryBuildDataSource = query.addDataSource(tableNum(CustTable));
    queryBuildRange = queryBuildDataSource.addRange(fieldNum(CustTable, CustGroup));
    queryBuildRange.value('40');
    sysTableLookup.parmQuery(query);
    sysTableLookup.performFormLookup();
    //super();
}