Quickly render a Sitecore Controller Rendering, using given Item as Datasource

RenderItem.cs

        public virtual HtmlString RenderItem(Item item, string controller, string action)
        {
            Assert.ArgumentNotNull(item, "item");
            Assert.ArgumentNotNullOrEmpty(controller, "controller");
            Assert.ArgumentNotNullOrEmpty(action, "action");
            var r = new Rendering();
            r.DataSource = item.Paths.FullPath;

            using (RenderingContext.EnterContext(r))
            {
                var runner = new ControllerRunner(controller, action);
                var result = runner.Execute();
                return new HtmlString(result);
            }
        }