BaseController.cs

namespace Something
{
    public class BaseController : Controller
    {
        #region partial rendering in controller

        public string RenderPartialToString(string partialViewName, object model)
        {
            InvalidateControllerContext();
            var view = ViewEngines.Engines.FindPartialView(ControllerContext, partialViewName).View;

            string result = RenderViewToString(view, model);
            return result;
        }

        public string RenderViewToString(string viewName, object model)
        {
            InvalidateControllerContext();
            var view = ViewEngines.Engines.FindView(ControllerContext, viewName, null).View;

            string result = RenderViewToString(view, model);
            return result;
        }

        public string RenderViewToString(IView view, object model)
        {
            InvalidateControllerContext();
            string result = null;

            if (view != null)
            {
                var sb = new StringBuilder();

                using (var writer = new StringWriter(sb))
                {
                    var viewContext = new ViewContext(ControllerContext, view, new ViewDataDictionary(model), new TempDataDictionary(), writer);

                    view.Render(viewContext, writer);
                    writer.Flush();
                }

                result = sb.ToString();
            }

            return result;
        }

        private void InvalidateControllerContext()
        {
            if (ControllerContext == null)
            {
                var context = new ControllerContext(System.Web.HttpContext.Current.Request.RequestContext, this);
                ControllerContext = context;
            }
        }

        #endregion
    }
}