stride3d/stride · error · ArgumentException

Extension contains invalid characters

Error message

Extension contains invalid characters

What it means

FileExtensionCollection.NormalizeExtension rejects extension strings containing characters that are invalid in file names (per Path.GetInvalidFileNameChars), other than '*'. This guards the collection against malformed extensions that could never match a real file.

Solutions

1. Strip invalid characters or pass only the extension portion (e.g. ".png")
2. Extract the extension with Path.GetExtension before adding
3. Sanitize user/config-supplied extension strings before registering them

Example fix

// before
collection.Add(Path.GetFileName("C:/icons/logo.png"));
// after
collection.Add(Path.GetExtension("C:/icons/logo.png"));

if (ext.Any(c => c != '*' && Path.GetInvalidFileNameChars().Contains(c))) throw new ArgumentException("Invalid chars in extension", nameof(ext));

try { collection.Add(ext); } catch (ArgumentException) { collection.Add(Path.GetExtension(ext)); }

When it happens

Trigger: Adding an extension containing characters like '\\', '/', ':', quotes, or other invalid filename characters, e.g. collection.Add("*.pn|g") or an extension pasted from a full path.

Common situations: Accidentally passing a full file path instead of an extension; typos or shell-escaped characters in configuration; Windows-invalid characters on cross-platform inputs.

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.

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Expecting a single extension
• 's must be finite and greater than zero
• Value must be > 0
• This method must be invoked with at least one property name.
• Cannot use as a list of digit

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/42a83fca0dbe93fe. Report an issue: GitHub.

Appendix: source

Thrown at sources/assets/Stride.Core.Assets/IO/FileExtensionCollection.cs:90

    private static List<string> SplitExtensions(string extensions)
    {
        return extensions.Split([';', ','], StringSplitOptions.RemoveEmptyEntries).Select(NormalizeExtension).ToList();
    }

    private static string NormalizeExtension(string extension)
    {
        ArgumentNullException.ThrowIfNull(extension);

        if (extension.Contains(';') || extension.Contains(','))
            throw new ArgumentException("Expecting a single extension");

        if (extension.StartsWith("*.", StringComparison.Ordinal))
        {
            extension = extension[1..];
        }
        if (extension.Any(x => x != '*' & Path.GetInvalidFileNameChars().Contains(x)))
            throw new ArgumentException("Extension contains invalid characters");

        if (!extension.StartsWith('.'))
        {
            extension = $".{extension}";
        }
        return extension.ToLowerInvariant();
    }
}

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