Dynamics Look Up Filter

Dynamics Look Up Filter 

One of my form's I want to display the purchase order numbers(in a drop down),whose status is "not invoiced"

Take a new form->new StringEdit control->lookup();
use the following code.
----

public void lookup()
{
PurchTable purchTable;
SysTableLookup sysTableLookup = SysTableLookup::newParameters(tablenum(PurchTable), this);
Query query = new Query();
QueryBuildDataSource queryBuildDataSource = query.addDataSource(tablenum(PurchTable));
;
sysTableLookup.addLookupfield(fieldnum(PurchTable, PurchId));
sysTableLookup.addLookupfield(fieldnum(PurchTable, PurchName));
sysTableLookup.addLookupfield(fieldnum(PurchTable,PurchStatus));
queryBuildDataSource.addRange(fieldnum(PurchTable, PurchStatus)).value(enum2str(PurchStatus::Backorder));
queryBuildDataSource.addRange(fieldnum(PurchTable, PurchStatus)).value(enum2str(PurchStatus::Received));
queryBuildDataSource.addRange(fieldnum(PurchTable, PurchStatus)).value(enum2str(PurchStatus::Canceled));
queryBuildDataSource.addRange(fieldnum(PurchTable, PurchStatus)).value(enum2str(PurchStatus::None));

sysTableLookup.parmQuery(query);
sysTableLookup.performFormLookup();
}
_______________________________________
To filter PurchId values
To avoid the null values in Dynamic lookup

public void lookup()
{
PurchTable purchTable;
SysTableLookup sysTableLookup = SysTableLookup::newParameters(tablenum(PurchTable), this);
Query query = new Query();
QueryBuildDataSource queryBuildDataSource = query.addDataSource(tablenum(PurchTable));
;
sysTableLookup.addLookupfield(fieldnum(PurchTable, PurchId));

queryBuildDataSource.addRange(fieldnum(PurchTable, PurchId)).value("000010..000020");
//To avoid the null values in Dynamic lookup
//queryBuildDataSource.addRange(fieldnum(Test_Vend,Name)).value(SysQuery::valueNotEmptyString());
//queryBuildDataSource.addRange(fieldnum(Test_Vend,Name)).value('!="" ');



sysTableLookup.parmQuery(query);
sysTableLookup.performFormLookup();
}