Return View as String in .NET Core

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If like me you have a number of controllers that need this, like in a reporting site, it’s not really ideal to repeat this code, and even injecting or calling another service doesn’t really seem right.

So I’ve made my own version of the above with the following differences:

  • model strong-typing
  • error checking when finding a view
  • ability to render views as partials or pages
  • asynchronus
  • implemented as a controller extension

  • no DI needed

    using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewEngines;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using System.IO;
using System.Threading.Tasks;

namespace CC.Web.Helpers
{
    public static class ControllerExtensions
    {
        public static async Task<string> RenderViewAsync<TModel>(this Controller controller, string viewName, TModel model, bool partial = false)
        {
            if (string.IsNullOrEmpty(viewName))
            {
                viewName = controller.ControllerContext.ActionDescriptor.ActionName;
            }

            controller.ViewData.Model = model;

            using (var writer = new StringWriter())
            {
                IViewEngine viewEngine = controller.HttpContext.RequestServices.GetService(typeof(ICompositeViewEngine)) as ICompositeViewEngine;
                ViewEngineResult viewResult = viewEngine.FindView(controller.ControllerContext, viewName, !partial);

                if (viewResult.Success == false)
                {
                    return $"A view with the name {viewName} could not be found";
                }

                ViewContext viewContext = new ViewContext(
                    controller.ControllerContext,
                    viewResult.View,
                    controller.ViewData,
                    controller.TempData,
                    writer,
                    new HtmlHelperOptions()
                );

                await viewResult.View.RenderAsync(viewContext);

                return writer.GetStringBuilder().ToString();
            }
        }
    }
}

Then just implement with:

viewHtml = await this.RenderViewAsync("Report", model);

Or this for a PartialView:

partialViewHtml = await this.RenderViewAsync("Report", model, true);

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