--- title: Utility components description: "The three Pennington.UI utility components — LanguageSwitcher, StructuredData, and FallbackNotice — their parameters and a one-line use-when row each." canonical_url: https://usepennington.net/reference/ui/utility/ sidecar_url: https://usepennington.net/reference/ui/utility.md content_hash: sha256:892f5c0654ca7cc25c57fe7e359205a6777f1c1163c3f68006159c4955f4475b tokens: 1229 uid: reference.ui.utility reading_time_minutes: 3 --- Reference # Utility components The three Pennington.UI utility components — LanguageSwitcher, StructuredData, and FallbackNotice — their parameters and a one-line use-when row each. `Pennington.UI` ships three utility Razor components — `LanguageSwitcher`, `StructuredData`, and `FallbackNotice` — that handle locale selection, JSON-LD head injection, and fallback-locale notification respectively. All three live in namespace `Pennington.UI.Components` and are made available via the `@using Pennington.UI.Components` import. ## `LanguageSwitcher` Renders a `

`-backed dropdown of alternate-language links configured for SPA reload via `data-spa-reload`. Hides itself when fewer than two locales are available. Auto-computes the list from `LocaleContext` and `LocalizationOptions` when `AlternateLanguages` is null or empty. ### Parameters Name Type Default Description `AlternateLanguages` `IReadOnlyList?` `null` Explicit list of alternate-language items; when null or empty, the component auto-computes the list from the injected `LocaleContext` and `LocalizationOptions`. ### `AlternateLanguageItem` Nested record type that callers supply when constructing an explicit `AlternateLanguages` list; `DocSite`'s `MainLayout` builds one instance per locale per-request from `DocSiteContentResolver.GetAlternateLanguagesAsync`. Name Type Description `Locale` `string` Locale code written to the `data-locale` attribute on the rendered ``. `DisplayName` `string` Visible label used in the dropdown row and as the currently-selected summary text. `Url` `string` `href` written on the anchor; typically a locale-prefixed canonical path. `IsCurrentLocale` `bool` When `true`, the row renders with current-locale styling (`font-semibold` and the primary accent color). ### Example ```razor @if (LocalizationOptions.IsMultiLocale) { } ``` ## `StructuredData` Emits one `