# IOpcType Interface

<span class="api-meta">since v2.8</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">IOpcType Members</a></dd>
<dt>Also in</dt>
<dd>Opc.UaFx.Client</dd>
</dl>

Represents type declarations used for objects, variables, events, references and data.

## Syntax

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

```csharp
public interface IOpcType
```

</div>

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

```vbnet
Public Interface IOpcType
```

</div>

## Derived types

- [OpcDataTypeInfo](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatatypeinfo/)
- [OpcNodeTypeInfo](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodetypeinfo/)
- [OpcObjectTypeInfo](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcobjecttypeinfo/)
- [OpcVariableTypeInfo](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcvariabletypeinfo/)

## Properties

| Name | Description |
|---|---|
| [Category](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.iopctype/members#category) | Gets the category the IOpcType falls within. |
| [IsUnknown](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.iopctype/members#isunknown)<span class="api-meta">since v2.9</span> | Gets a value indicating whether the IOpcType acts as a placeholder for a referenced type its type declaration could not resolved. |
| [Name](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.iopctype/members#name) | Gets a value which defines the non-localizable human-readable name of the type represented. |
| [TypeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.iopctype/members#typeid) | Gets a value which identifies the type represented. |
| [UnderlyingType](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.iopctype/members#underlyingtype) | Gets the type which provides the implementation of the type declaration. |

## Applies to

| Package | Versions |
|---|---|
| Opc.UaFx.Advanced | v2.8–v2.59 |