stride3d/stride · error · ArgumentException

The value must be an Index when type is ElementType.Index.

Error message

The value must be an Index when type is ElementType.Index.

What it means

GraphNodePath.PushElement throws ArgumentException when ElementType.Index is requested but the value is not a NodeIndex. Index segments must be Quantum NodeIndex instances so they can represent both list indices and dictionary keys uniformly.

Solutions

1. Wrap the index/key in NodeIndex before pushing (NodeIndex.New(value))
2. Use the typed PushIndex(NodeIndex) helper
3. Convert int indices via NodeIndex.New(i) and dictionary keys likewise
4. Catch ArgumentException and validate the element type in generic path builders

Example fix

// before
path.Push(3, ElementType.Index);
// after
path.PushIndex(NodeIndex.New(3));

if (elementValue is not NodeIndex) throw new ArgumentException("Index path element must be a NodeIndex");

bool IsIndexElement(object? v) => v is NodeIndex;

try { path.Push(value, ElementType.Index); } catch (ArgumentException ex) { logger.LogError(ex, "Invalid index path element"); }

When it happens

Trigger: Calling Push/PushIndex with a raw int, string key, or other type instead of a NodeIndex when pushing an ElementType.Index segment.

Common situations: Passing plain integers from UI code into path builders; forgetting to wrap dictionary keys in NodeIndex.New(key); copying path code that used ints.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Expecting relative path
• filePath must be relative
• Invalid relative path. Expecting an absolute project path
• The value must be a non-null string when type is…
• The value must be null when type is ElementType.Target.

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/25bc919bff4e0c5d. Report an issue: GitHub.

Appendix: source

Thrown at sources/presentation/Stride.Core.Quantum/GraphNodePath.cs:451

    }

    private void PushElement(object? elementValue, ElementType type)
    {
        switch (type)
        {
            case ElementType.Member:
                if (elementValue is not string name)
                    throw new ArgumentException("The value must be a non-null string when type is ElementType.Member.");
                path.Add(NodePathElement.CreateMember(name));
                break;
            case ElementType.Target:
                if (elementValue != null)
                    throw new ArgumentException("The value must be null when type is ElementType.Target.");
                path.Add(NodePathElement.CreateTarget());
                break;
            case ElementType.Index:
                if (!(elementValue is NodeIndex))
                    throw new ArgumentException("The value must be an Index when type is ElementType.Index.");
                path.Add(NodePathElement.CreateIndex((NodeIndex)elementValue));
                break;
            default:
                throw new ArgumentOutOfRangeException(nameof(type));
        }
    }
}

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