OrchardCMS/OrchardCore · error · PluralFormNotFoundException

Plural form ' ' doesn't exist for the key ' ' in the ' '…

Error message

Plural form '{pluralForm}' doesn't exist for the key '{key}' in the '{CultureName}' culture.

What it means

CultureDictionary stores translations per plural form; when a caller requests a translation with a count whose computed plural rule index exceeds the stored translations array, the dictionary throws PluralFormNotFoundException. This indicates the PO/translation source does not provide all plural forms required by the culture's plural rule (e.g. only 2 forms stored for a culture needing 3).

Solutions

Fix the translation source (PO file) so the key includes all plural forms required by the culture.
Catch PluralFormNotFoundException and fall back to form 0 or the default string.
Regenerate/validate translations with the culture's nplurals rule before importing.
If you control the lookup, omit count so pluralForm resolves to 0 when a full set is unavailable.

Example fix

// before (PO msgstr with only 2 forms for a 3-form culture)
msgstr[0] "..."; msgstr[1] "..."
// after
msgstr[0] "..."; msgstr[1] "..."; msgstr[2] "..."

Defensive patterns

Strategy: try-catch

Validate before calling

var translations = dictionary[key]; // validate count of forms loaded
if (translations?.Length <= culturePluralFormsCount) logger.LogWarning("Key {Key} missing plural forms for {Culture}", key, culture.Name);

Try / catch

try { text = dictionary[key, count]; }
catch (PluralFormNotFoundException ex) { logger.LogWarning(ex, "Missing plural form; using fallback"); text = dictionary[key] ?? key; }

Prevention

Validate PO files cover all nplurals forms per culture before import
Test localization for all supported cultures with counts 0..5
Keep translations complete when adding new cultures

When it happens

Trigger: Accessing CultureDictionary indexer with a count whose PluralRule(count) returns an index >= translations.Length for the key, typically due to incomplete plural translations for languages with multiple plural forms.

Common situations: Importing PO files with missing plural entries, switching the site to a culture (Russian, Polish, Arabic) whose plural rule needs more forms than the translation provides, or hand-written translations omitting nplurals entries.

Related errors

AI-assisted analysis of OrchardCMS/OrchardCore@4306c0717f (2026-09-13). Data as JSON: /api/errors/952ac856b94377c1. Report an issue: GitHub.

Appendix: source

Thrown at src/OrchardCore/OrchardCore.Localization.Abstractions/CultureDictionary.cs:59

    /// <summary>
    /// Gets the localized value.
    /// </summary>
    /// <param name="key">The resource key.</param>
    /// <param name="count">The number to specify the pluralization form.</param>
    /// <returns></returns>
    public string this[CultureDictionaryRecordKey key, int? count]
    {
        get
        {
            if (!Translations.TryGetValue(key, out var translations))
            {
                return null;
            }

            var pluralForm = count.HasValue ? PluralRule(count.Value) : 0;
            if (pluralForm >= translations.Length)
            {
                throw new PluralFormNotFoundException($"Plural form '{pluralForm}' doesn't exist for the key '{key}' in the '{CultureName}' culture.", new PluralForm(key, pluralForm, CultureInfo.GetCultureInfo(CultureName)));
            }

            return translations[pluralForm];
        }
    }

    /// <summary>
    /// Gets a list of the culture translations including the plural forms.
    /// </summary>
    public IDictionary<CultureDictionaryRecordKey, string[]> Translations { get; }

    /// <summary>
    /// Merges the translations from multiple dictionary records.
    /// </summary>
    /// <param name="records">The records to be merged.</param>
    public void MergeTranslations(IEnumerable<CultureDictionaryRecord> records)
    {
        foreach (var record in records)

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