# OpcNodeHistorian Class

> Reference: Provides and maintains the history of the values of an OpcVariableNode in memory.

<dl class="api-definition">
<dt>Namespace</dt>
<dd><a href="../namespaces/opc.uafx.server">Opc.UaFx.Server</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">OpcNodeHistorian Members</a></dd>
</dl>

Provides and maintains the history of the values of an [OpcVariableNode](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcvariablenode/) in memory.

## Syntax

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

```csharp
public class OpcNodeHistorian
```

</div>

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

```vbnet
Public Class OpcNodeHistorian
```

</div>

## Inheritance

[Object](https://learn.microsoft.com/dotnet/api/system.object) → **OpcNodeHistorian**

## Implements

<ul class="api-implements">
<li><a href="../opc.uafx.server.iopcnodehistoryprovider/">IOpcNodeHistoryProvider</a></li>
</ul>

## Remarks

The node manager uses the historian for the history services of the node if [RetrieveNodeHistoryProvider](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/members#retrievenodehistoryprovider) returns the historian for the node.

## Constructors

| Name | Description |
|---|---|
| [OpcNodeHistorian](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#opcnodehistorian)<span class="api-meta">3 overloads</span> | Initializes a new instance of the OpcNodeHistorian class using the `owner` and `node` specified. |

## Properties

| Name | Description |
|---|---|
| [AutoUpdateHistory](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#autoupdatehistory) | Gets or sets a value indicating whether the historian adds the value of the [Node](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#node) to the [History](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#history) whenever the value of the node changes. |
| [History](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#history) | Gets the history of the values of the [Node](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#node). |
| [ModifiedHistory](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#modifiedhistory) | Gets the history of the modifications of the [History](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#history) through the history services. |
| [Node](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#node) | Gets the node whose history the historian maintains. |
| [Owner](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#owner) | Gets the node manager which provides the [Node](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#node). |
| [SyncRoot](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#syncroot) | Gets the object used to synchronize the access to the historian. |

## Methods

| Name | Description |
|---|---|
| [CreateHistory](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#createhistory) |  |
| [DeleteHistory](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#deletehistory)<span class="api-meta">3 overloads</span> |  |
| [ReadHistory](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#readhistory)<span class="api-meta">since v2.51</span> |  |
| [ReplaceHistory](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#replacehistory) |  |
| [UpdateHistory](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodehistorian/members#updatehistory) |  |

## Applies to

| Package | Versions |
|---|---|
| Opc.UaFx.Advanced | v2.5–v2.59 |