Umbraco-CMS/src/Umbraco.Infrastructure/Persistence/Repositories/Implement/LanguageRepositoryExtensions.cs

using Umbraco.Cms.Core;
using Umbraco.Cms.Core.Persistence.Repositories;

namespace Umbraco.Core.Persistence.Repositories.Implement
{
    internal static class LanguageRepositoryExtensions
    {
        public static bool IsDefault(this ILanguageRepository repo, string culture)
        {
            if (culture == null || culture == "*") return false;
            return repo.GetDefaultIsoCode().InvariantEquals(culture);
        }
    }
}