# OpcModellingDirective Enum

> Reference: Specifies how a node handles one of its child nodes according to its node model (see OpcNodeModel).

<span class="api-meta">since v2.50</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>
</dl>

Specifies how a node handles one of its child nodes according to its node model (see [OpcNodeModel](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodemodel/)).

## Syntax

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

```csharp
public enum OpcModellingDirective
```

</div>

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

```vbnet
Public Enum OpcModellingDirective
```

</div>

## Inheritance

[Object](https://learn.microsoft.com/dotnet/api/system.object) → [ValueType](https://learn.microsoft.com/dotnet/api/system.valuetype) → [Enum](https://learn.microsoft.com/dotnet/api/system.enum) → **OpcModellingDirective**

## Fields

| Name | Value | Description |
|---|---|---|
| <a id="create"></a>`Create` | `1` | The child node is created if it does not exist. A node model with the modelling rule [Mandatory](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmodellingrule/#mandatory) or [MandatoryPlaceholder](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmodellingrule/#mandatoryplaceholder) uses this directive. |
| <a id="default"></a>`Default` | `0` | The child node is neither created nor removed. |
| <a id="omit"></a>`Omit` | `2` | The child node is removed if it exists. |

## Applies to

| Package | Versions |
|---|---|
| Opc.UaFx.Advanced | v2.50–v2.59 |