BlogPostUrlProvider

BlogPostUrlProvider.cs

public class BlogPostUrlProvider : IUrlProvider
{
    public IEnumerable<string> GetOtherUrls(UmbracoContext umbracoContext, int id, Uri current)
    {
        return Enumerable.Empty<string>();
    }

    public string GetUrl(UmbracoContext umbracoContext, int id, Uri current, UrlProviderMode mode)
    {
        var content = umbracoContext.ContentCache.GetById(id);
        if (content == null || content.DocumentTypeAlias != "blogPostPage")
        {
            return null;
        }

        var blogRootUrl = umbracoContext.UrlProvider.GetUrl(content.Parent.Id, current, mode);
        var category = content.GetPropertyValue<string>("category")?.Slug();
        return $"{blogRootUrl}{category}/{content.UrlName}";
    }
}

RegisterBlogPostUrlProviderEvent.cs

public class RegisterBlogPostUrlProviderEvent : ApplicationEventHandler
{
    protected override void ApplicationStarting(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
    {
        UrlProviderResolver.Current.InsertTypeBefore<DefaultUrlProvider, BlogPostUrlProvider>();
    }
}