Company Lookup for an Unbounded Control in D365FO

 In D365FO, you can create a Company (DataArea) lookup for an unbounded control using SysTableLookup without requiring any datasource binding.

[FormControlEventHandler(formControlStr(PurchCreateFromSalesOrder, DSS_IntercompanyId), 
FormControlEventType::Lookup)]
public static void DSS_IntercompanyId_OnLookup(FormControl sender, FormControlEventArgs e)
{
    SysTableLookup       sysTableLookup;
    Query                query;
    QueryBuildDataSource qbds;

    sysTableLookup = SysTableLookup::newParameters(tableNum(CompanyInfo), sender);

    sysTableLookup.addLookupfield(fieldNum(CompanyInfo, DataArea));
    sysTableLookup.addLookupfield(fieldNum(CompanyInfo, Name));

    query = new Query();
    qbds  = query.addDataSource(tableNum(CompanyInfo));

    // Optional filter
    // qbds.addRange(fieldNum(CompanyInfo, DataArea))
    //     .value(SysQuery::valueNotEquals(curExt()));

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

Key Point

Use CompanyInfo to display available companies/legal entities and pass sender to SysTableLookup::newParameters() for the unbounded control.