Use language tags

The Bcp47LanguageTag type is an implementation of IETF language tags as defined by BCP 47; it supports the composition and deconstruction of language tags from strings or using a fluent-style builder.

Create a language tag

You can create language tags using factory methods on the Bcp47LanguageTag type. For example,

Bcp47LanguageTag languageTag;
languageTag = Bcp47LanguageTag.Create("en");        // English
languageTag = Bcp47LanguageTag.Create("mas");       // Maasai
languageTag = Bcp47LanguageTag.Create("fr-CA");     // French as used in Canada
languageTag = Bcp47LanguageTag.Create("es-419");    // Spanish as used in Latin America
languageTag = Bcp47LanguageTag.Create("zh-Hans");   // Chinese written with Simplified script

Language tags created in this way have validation applied to the source tag using rules based on codes implemented by other Data Standardizer packages. If an attempt is made to create a language tag object with an invalid source tag then an exception (LanguageTagFormatException) will be thrown.

The standard for language tags also specifies that the range of valid tags can be defined or constrained by the IANA Language Subtag Registry. You can load an instance of the registry from an external source and then use this to validate what constitutes a valid language tag. For example,

var subtagRegistry = SubtagRegistry.CreateFromFile("subtag_registry.txt");
var languageTag = Bcp47LanguageTag.Create("en", subtagRegistry);

If you would rather avoid exceptions for invalid input, the type also provides TryCreate overloads that return false instead of throwing.

Validate tags

You can validate a tag or subtags without having to try to create the tag. If you want to check whether a string contains a valid, full language tag, you can call the IsWellFormedLanguageTagString() method:

var isValidTag = Bcp47LanguageTag.IsWellFormedLanguageTagString("Not_A_Valid_Tag"); // returns false

Subtags can also be checked. For example,

bool isValid;
isValid = Bcp47LanguageTag.CheckPrimaryLanguageSubtag("en");    // English
isValid = Bcp47LanguageTag.CheckExtendedLanguageSubtag("xxx");
isValid = Bcp47LanguageTag.CheckScriptSubtag("Cyrl");           // Cyrillic
isValid = Bcp47LanguageTag.CheckRegionSubtag("419");            // Latin America and the Caribbean
isValid = Bcp47LanguageTag.CheckVariantSubtag("1606nict");      // Late Middle French
isValid = Bcp47LanguageTag.CheckExtensionSubtag("u-Latn");
isValid = Bcp47LanguageTag.CheckPrivateUseSubtag("x-private");

Extract subtags

The subtags that comprise a language tag object can be extracted from the language tag using properties for access to the raw subtag values, or methods for conversion of the subtags to members of the relevant enums.

var languageTag = Bcp47LanguageTag.Create("gsw-u-sd-chzh");
var primaryLanguageSubtag = languageTag.ToIso639Part3();
var extensionSubtags = languageTag.ExtensionSubtags;

For more on the parts that make up a tag, see Anatomy of a language tag.

Use language tags

Create a language tag

Validate tags

Extract subtags

Related