Kentico Xperience Page Template Filter base class

DefaultPageTemplateFilter.cs

/// <summary>
/// Default filter for associating Page Types to Page Templates
/// </summary>
public abstract class DefaultPageTemplateFilter : IPageTemplateFilter
{
    /// <summary>
    /// If true, then the templates returned by <see cref="FilterBy(PageTemplateDefinition)"/> are excluded from the results of <see cref="Filter(IEnumerable{PageTemplateDefinition}, PageTemplateFilterContext)"/>
    /// when the <see cref="PageTypeClassName"/> does not match the Page Type of the context.
    /// Defaults to false.
    /// </summary>
    public virtual bool ExcludeIfNoMatch { get; } = false;

    /// <summary>
    /// The prefix of the <see cref="RegisterComponentAttribute.Identifier"/> of the given Page Template on which to match
    /// </summary>
    public abstract string PageTemplatePrefix { get; }

    /// <summary>
    /// The <see cref="TreeNode.ClassName"/> used to compare to the <see cref="PageTemplateFilterContext.PageType"/>
    /// </summary>
    public abstract string PageTypeClassName { get; }

    public IEnumerable<PageTemplateDefinition> Filter(IEnumerable<PageTemplateDefinition> pageTemplates, PageTemplateFilterContext context)
    {
        if (context.PageType.Equals(PageTypeClassName, StringComparison.InvariantCultureIgnoreCase))
        {
            return pageTemplates.Where(FilterBy);
        }

        if (ExcludeIfNoMatch)
        {
            return pageTemplates.Where(t => !FilterBy(t));
        }

        return pageTemplates;
    }

    /// <summary>
    /// By default this matches if the definition Identifier starts with the <see cref="PageTemplatePrefix"/>
    /// </summary>
    /// <param name="definition"></param>
    /// <returns></returns>
    protected virtual bool FilterBy(PageTemplateDefinition definition) =>
        definition.Identifier.StartsWith(PageTemplatePrefix, StringComparison.OrdinalIgnoreCase);
}

HomePageTemplateFilter.cs

public class HomePageTemplateFilter : DefaultPageTemplateFilter
{
    public override string PageTemplatePrefix => "Sandbox_Home_";

    public override string PageTypeClassName => HomePage.CLASS_NAME;
}

ServiceCollectionExtensions.cs

public static class ServiceCollectionExtensions
{
    /// <summary>
    /// Adds all existing Page Template Filters to the <see cref="PageBuilderFilters.PageTemplates"/> via reflection
    /// </summary>
    /// <param name="services"></param>
    /// <param name="assembiles"></param>
    /// <returns></returns>
    /// <example>
    /// services.AddPageTemplateFilters(Assembly.GetExecutingAssembly())
    /// </example>
    public static IServiceCollection AddPageTemplateFilters(this IServiceCollection services, params Assembly[] assembiles)
    {
        var types = assembiles.SelectMany(a => a.GetExportedTypes()
            .Where(t => !t.IsAbstract && !t.IsInterface && t.IsAssignableTo(typeof(IPageTemplateFilter))));

        foreach (var t in types)
        {
            object? instance = Activator.CreateInstance(t);

            if (instance is IPageTemplateFilter filter)
            {
                PageBuilderFilters.PageTemplates.Add(filter);
            }
        }

        return services;
    }
}