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DBCon

property DBCon: TvxDBCon read;

Example​

procedure RequirePrimaryConnection(const Data: TvxDBDef);
begin
  if Data.DBConCount = 0 then
    raise Exception.Create('No database connection is configured');
  if Data.DBCon = nil then
    raise Exception.Create('The primary database connection did not load');
end;

Usage​

DBCon returns the database connection behind the first database link, loading on first access it and failing when no first link exists.

  • Check DBConCount > 0 before access, then check the returned object for nil.
  • Use DBCons when a data definition contains multiple connections and the intended one is not explicitly known to be first.
  • Do not retain the reference beyond the owning data definition's lifetime.

Additional Technical Info​

DBCon is a convenience alias for the concrete TvxDBCon owned by DBCons[0]. It does not search for an active or writable connection.

Source-backed behaviour​

The PascalScript runtime helper evaluates Self.DBCons[0].DBCon directly. There is no DBConCount guard, so reading this property when the link list is empty raises a list-index exception.

The first object is a TvxDBLink, not necessarily an already loaded connection. Its DBCon getter lazily creates a TvxDBCon, calls LoadModule with the link GUID and frees it again if ModuleLoaded remains false. Load exceptions are caught and logged by the link; the property can consequently return nil. Reading can therefore allocate objects, query configuration data and add log entries.

The choice of index zero is configuration order. It is unrelated to connection name, active state or transaction state.

Created 2026-07-15