Umbraco-CMS/src/Umbraco.Web.Common/Extensions/BlockListTemplateExtensions.cs

using System;
using Microsoft.AspNetCore.Html;
using Microsoft.AspNetCore.Mvc.Rendering;
using Umbraco.Cms.Core.Models.Blocks;
using Umbraco.Cms.Core.Models.PublishedContent;

namespace Umbraco.Extensions
{
    public static class BlockListTemplateExtensions
    {
        public const string DefaultFolder = "blocklist/";
        public const string DefaultTemplate = "default";

        public static IHtmlContent GetBlockListHtml(this IHtmlHelper html, BlockListModel model, string template = DefaultTemplate)
        {
            if (model?.Count == 0) return new HtmlString(string.Empty);

            var view = DefaultFolder + template;
            return html.Partial(view, model);
        }

        public static IHtmlContent GetBlockListHtml(this IHtmlHelper html, IPublishedProperty property, string template = DefaultTemplate) => GetBlockListHtml(html, property?.GetValue() as BlockListModel, template);

        public static IHtmlContent GetBlockListHtml(this IHtmlHelper html, IPublishedContent contentItem, string propertyAlias) => GetBlockListHtml(html, contentItem, propertyAlias, DefaultTemplate);

        public static IHtmlContent GetBlockListHtml(this IHtmlHelper html, IPublishedContent contentItem, string propertyAlias, string template)
        {
            if (propertyAlias == null) throw new ArgumentNullException(nameof(propertyAlias));
            if (string.IsNullOrWhiteSpace(propertyAlias)) throw new ArgumentException("Value can't be empty or consist only of white-space characters.", nameof(propertyAlias));

            var prop = contentItem.GetProperty(propertyAlias);
            if (prop == null) throw new InvalidOperationException("No property type found with alias " + propertyAlias);

            return GetBlockListHtml(html, prop?.GetValue() as BlockListModel, template);
        }
    }
}