# IOpcTypeSystem Interface

<span class="api-meta">since v2.9</span>

<dl class="api-definition">
<dt>Namespace</dt>
<dd><a href="../namespaces/opc.uafx">Opc.UaFx</a></dd>
<dt>Assembly</dt>
<dd>Opc.UaFx.Advanced.dll</dd>
<dt>Package</dt>
<dd>Opc.UaFx.Advanced v2.59.0</dd>
<dt>Members</dt>
<dd><a href="./members">IOpcTypeSystem Members</a></dd>
<dt>Also in</dt>
<dd>Opc.UaFx.Client</dd>
</dl>

Provides type information used within a specific scope of OPC UA.

## Syntax

<div class="api-signature" data-lang="csharp">

```csharp
public interface IOpcTypeSystem
```

</div>

<div class="api-signature" data-lang="vbnet">

```vbnet
Public Interface IOpcTypeSystem
```

</div>

## Base interfaces

<ul class="api-implements">
<li><a href="../opc.uafx.iopctypeprovider/">IOpcTypeProvider</a></li>
</ul>

## Derived types

- [OpcDataTypeSystem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatatypesystem/)
- [OpcNodeTypeSystem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodetypesystem/)
- [OpcTypeSystem&lt;T&gt;](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opctypesystem-1/)

## Properties

| Name | Description |
|---|---|
| [FallbackTypeSystem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.iopctypesystem/members#fallbacktypesystem) | Gets the type system used as the fallback system to query type information which is referenced in the current IOpcTypeSystem but is not declared. |
| [IsEmpty](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.iopctypesystem/members#isempty) | Gets a value indicating whether the current IOpcTypeSystem represents a type system to use if there is no specific type system described. |
| [Scope](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.iopctypesystem/members#scope) | Gets the scope of types covered by the current IOpcTypeSystem. |

Inherits members from [IOpcTypeProvider](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.iopctypeprovider/members).

## Applies to

| Package | Versions |
|---|---|
| Opc.UaFx.Advanced | v2.9–v2.59 |