AX 2012: Create lookup in X++

To create a lookup on a control (e.g. StringEdit control), override the lookup method of that control and copy paste the following code snippet in it. Of course, you will need to substitute datasource of the query according to your requirements.

public void lookup()
{
    Query query;
    QueryBuildDataSource datasourceModule;
    QueryBuildDataSource datasourceLanguage;
    QueryBuildRange rangeElementType;
    QueryBuildRange rangeModuleId;
    SysTableLookup sysTableLookup;
 
    query = new Query();
    datasourceLanguage = query.addDataSource(tableNum(SysModelElement));
    datasourceModule = datasourceLanguage.addDataSource(tableNum(SysModelElement));
    datasourceModule.joinMode(JoinMode::InnerJoin);
    datasourceModule.relations(false);
    datasourceModule.addLink(
        fieldNum(SysModelElement, ParentModelElement),
        fieldNum(SysModelElement, RecId));

    datasourceModule.addRange(
        fieldNum(SysModelElement, ElementType)).value(int2str(UtilElementType::LabelFile));

    datasourceModule.addRange(fieldNum(SysModelElement, Name)).value(ModuleId.text());
 
    sysTableLookup = SysTableLookup::newParameters(tableNum(SysModelElement), this);
    sysTableLookup.addLookupfield(fieldNum(SysModelElement, Name));
    sysTableLookup.parmQuery(query);
    sysTableLookup.performFormLookup();
}