# API Changes in v2.21

> Reference: API changes of Opc.UaFx.Advanced in v2.21: 1 added, 0 removed, 0 changed, 0 obsoleted.

<dl class="api-definition">
<dt>Release</dt>
<dd>v2.21.0</dd>
<dt>Compared with</dt>
<dd>v2.20.4</dd>
<dt>Package</dt>
<dd>Opc.UaFx.Advanced</dd>
</dl>

## Added

### Opc.UaFx

| Symbol | Signature |
|---|---|
| [OpcDataTypeSystem.FallbackDataTypeSystem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatatypesystem/members#fallbackdatatypesystem) | `public OpcDataTypeSystem FallbackDataTypeSystem { get; }` |