MVC Controller Extension Method that allos for rendering a view to a string for usage in AJAX scenarios.

RenderingExtensions.cs

using System.IO;
using System.Web.Mvc;

namespace TheCodeAttic.Foundation.Extensions
{
    public static class RenderingExtensions
    {
        public static string RenderViewToString<TModel>(this Controller controller, string viewName, TModel model, bool partial = false)
        {
            var controllerContext = controller.ControllerContext;
            controllerContext.Controller.ViewData.Model = model;

            // To be or not to be (partial)
            var viewResult = partial ? ViewEngines.Engines.FindPartialView(controllerContext, viewName) : ViewEngines.Engines.FindView(controllerContext, viewName, null);

            StringWriter stringWriter;

            using (stringWriter = new StringWriter())
            {
                var viewContext = new ViewContext(
                    controllerContext,
                    viewResult.View,
                    controllerContext.Controller.ViewData,
                    controllerContext.Controller.TempData,
                    stringWriter);

                viewResult.View.Render(viewContext, stringWriter);
                viewResult.ViewEngine.ReleaseView(controllerContext, viewResult.View);
            }

            return stringWriter.ToString();
        }
    }
}

RenderViewToString-Example.cs

[HttpPost]
public JsonResult PerformLocationSearch()
{
    var searchParams = new LocationSearchParameters();

    if (searchParams.SearchParamsExist)
    {
        int totalResult = 0;
        var searchResults = _locationSearchHelper.PerformLocationSearch(searchParams, out totalResult).ToList();
        if (searchResults != null && searchResults.Any())
        {
            var htmlstring = this.RenderViewToString("~/Views/LocationSearch/_LocationSearchResults.cshtml", searchResults, true);

            return Json(new { resultCode = true,
                html = htmlstring,
                totalresults = totalResult,
                currentpage = searchParams.RequestedPage,
                msg = $"search has occurred, total results: {totalResult}" }, JsonRequestBehavior.AllowGet);
        }
    }

    return Json(new { resultCode = false, msg = "no results found", html = "<h3>No Results</h3>" }, JsonRequestBehavior.AllowGet);
}