Add optional parent-child linking when importing NodeSet2.xml

[Copilot]

Proposed changes

When importing nodes from NodeSet2.xml using UANodeSet.Import(), parent-child relationships were not established. This caused GetChildren() to return empty and prevented proper hierarchy navigation.

Root cause: The import process stored ParentNodeId in the Handle property but never established the bidirectional parent-child relationship in memory.

Solution: Added post-processing step that:

• Reads ParentNodeId from Handle property on imported nodes
• Sets Parent property on child nodes
• Adds children to parent's internal collection via AddChild()
• Feature is opt-in via linkParentChild parameter (defaults to false for backward compatibility)

Example usage:

var nodeSet = UANodeSet.Read(stream);
var nodes = new NodeStateCollection();

// Enable parent-child linking (new opt-in feature)
nodeSet.Import(context, nodes, linkParentChild: true);

// GetChildren() now works correctly
var parentNode = nodes.First(n => n.BrowseName.Name == "ParentObject");
var children = new List<BaseInstanceState>();
parentNode.GetChildren(context, children);  // Returns child nodes

// Default behavior (backward compatible)
nodeSet.Import(context, nodes);  // No parent-child links established

Changes:

• UANodeSetHelpers.cs: Added LinkParentChildRelationships() method, integrated into Import() with optional linkParentChild parameter (defaults to false)
• UANodeSetHelpersTests.cs: Added ParentChildReferencesTest() verifying hierarchy navigation when enabled, and ParentChildReferencesDefaultBehaviorTest() verifying backward compatibility

Related Issues

• Addresses issue where GetChildren() returns empty after importing nodes from NodeSet2.xml files

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Enhancement (non-breaking change which adds functionality)
• Test enhancement (non-breaking change to increase test coverage)
• Breaking change (fix or feature that would cause existing functionality to not work as expected, requires version increase of Nuget packages)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc.
• I have signed the CLA.
• I ran tests locally with my changes, all passed.
• I fixed all failing tests in the CI pipelines.
• I fixed all introduced issues with CodeQL and LGTM.
• I have added tests that prove my fix is effective or that my feature works and increased code coverage.
• I have added necessary documentation (if appropriate).
• Any dependent changes have been merged and published in downstream modules.

Further comments

The feature is opt-in to maintain backward compatibility. Default behavior is unchanged - parent-child relationships are NOT established unless explicitly requested via the linkParentChild parameter. This ensures existing code continues to work without modifications. All 7 UANodeSetHelpersTests pass, including new tests verifying both the feature functionality and backward compatibility.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Missing parent-child references when importing nodes</issue_title>
<issue_description>### Type of issue

• Bug
• Enhancement
• Compliance
• Question
• Help wanted

Current Behavior

When importing nodes from a NodeSet2.xml nodeset and adding those nodes to the server using AddPredefinedNode(SystemContext, node) in the custom nodemanager, the parent-child references are missing. As a result methods such as node.GetChildren() are not working.

Right now I can use a workaround with currentNode?.GetReferences(nodeManager?.SystemContext, references) and filter for the expected children manually.

Expected Behavior

The parent-child references should be present when importing nodesets and adding predefined nodes.

Steps To Reproduce

No response

Environment

- OS: Windows 10, Windows 11
- Environment: Visual Studio Code 1.99.3
- Runtime: NET9.0
- Nuget Version: 1.5.375.457
- Component:
- Server: -
- Client: -

Anything else?

I use the CustomNodeManager2 class with:

nodeSet.Import(SystemContext, predefinedNodes);

foreach (var node in predefinedNodes)
  {
      AddPredefinedNode(SystemContext, node);
  }
AddReverseReferences(externalReferences);

Is this behavior expected?</issue_description>

Comments on the Issue (you are @copilot in this section)

@salihgoncu Hello, Are the parent-child relationships defined properly in the nodeset2.xml file? Could you provide us a sample xml that shows the behavior in question?

Best Regards,
Salih</comment_new>

• Fixes Missing parent-child references when importing nodes #3068

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