'Render Razor View to string in ASP.NET Core

I use RazorEngine for parsing of templates in my MVC 6 project like this:

Engine.Razor.RunCompile(File.ReadAllText(fullTemplateFilePath), templateName, null, model);

It works fine for the beta 6. It does not work after upgrading to beta 7 with the error:

MissingMethodException: Method not found: "Void Microsoft.AspNet.Razor.CodeGenerators.GeneratedClassContext.set_ResolveUrlMethodName(System.String)". in RazorEngine.Compilation.CompilerServiceBase.CreateHost(Type templateType, Type modelType, String className)

This is global.json:

{
  "projects": [ "src", "test" ],
  "sdk": {
    "version": "1.0.0-beta7",
    "runtime": "clr",
    "architecture": "x64"
  }
}

This is project.json:

...
"dependencies": {
    "EntityFramework.SqlServer": "7.0.0-beta7",
    "EntityFramework.Commands": "7.0.0-beta7",
    "Microsoft.AspNet.Mvc": "6.0.0-beta7",
    "Microsoft.AspNet.Mvc.TagHelpers": "6.0.0-beta7",
    "Microsoft.AspNet.Authentication.Cookies": "1.0.0-beta7",
    "Microsoft.AspNet.Authentication.Facebook": "1.0.0-beta7",
    "Microsoft.AspNet.Authentication.Google": "1.0.0-beta7",
    "Microsoft.AspNet.Authentication.MicrosoftAccount": "1.0.0-beta7",
    "Microsoft.AspNet.Authentication.Twitter": "1.0.0-beta7",
    "Microsoft.AspNet.Diagnostics": "1.0.0-beta7",
    "Microsoft.AspNet.Diagnostics.Entity": "7.0.0-beta7",
    "Microsoft.AspNet.Identity.EntityFramework": "3.0.0-beta7",
    "Microsoft.AspNet.Server.IIS": "1.0.0-beta7",
    "Microsoft.AspNet.Server.WebListener": "1.0.0-beta7",
    "Microsoft.AspNet.StaticFiles": "1.0.0-beta7",
    "Microsoft.AspNet.Tooling.Razor": "1.0.0-beta7",
    "Microsoft.Framework.Configuration.Abstractions": "1.0.0-beta7",
    "Microsoft.Framework.Configuration.Json": "1.0.0-beta7",
    "Microsoft.Framework.Configuration.UserSecrets": "1.0.0-beta7",
    "Microsoft.Framework.Logging": "1.0.0-beta7",
    "Microsoft.Framework.Logging.Console": "1.0.0-beta7",
    "Microsoft.VisualStudio.Web.BrowserLink.Loader": "14.0.0-beta7",
    "RazorEngine": "4.2.2-beta1"
  },
...
  "frameworks": {
    "dnx451": { }
  },
...

My template is:

@model dynamic
@{
    Layout = null;
}

<!DOCTYPE html>

<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="utf-8" />
    <title>Registration</title>
</head>
<body>
<p>
    Hello, @Model
</p>
</body>
</html>

Does anyone have similar problems? There is another way to parse templates in MVC 6?

Solution 1:^[1]

I found this thread which discusses it: https://github.com/aspnet/Mvc/issues/3091

Someone in the thread created a sample service here: https://github.com/aspnet/Entropy/blob/dev/samples/Mvc.RenderViewToString/RazorViewToStringRenderer.cs

After trial and error I was able to trim the service down so it only needs a valid HttpContext and a ViewEngine and I added an overload that doesn't require a model. Views are relative to your application root (they don't have to live in a Views folder).

You will need to register the service in Startup.cs and also register HttpContextAccessor:

//Startup.cs ConfigureServices()
services.AddTransient<ViewRenderService>();
services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using System;
using System.IO;

namespace LibraryApi.Services
{
    public class ViewRenderService
    {
        IRazorViewEngine _viewEngine;
        IHttpContextAccessor _httpContextAccessor;

        public ViewRenderService(IRazorViewEngine viewEngine, IHttpContextAccessor httpContextAccessor)
        {
            _viewEngine = viewEngine;
            _httpContextAccessor = httpContextAccessor;
        }

        public string Render(string viewPath)
        {
            return Render(viewPath, string.Empty);
        }

        public string Render<TModel>(string viewPath, TModel model)
        {
            var viewEngineResult = _viewEngine.GetView("~/", viewPath, false);

            if (!viewEngineResult.Success)
            {
                throw new InvalidOperationException($"Couldn't find view {viewPath}");
            }

            var view = viewEngineResult.View;

            using (var output = new StringWriter())
            {
                var viewContext = new ViewContext();
                viewContext.HttpContext = _httpContextAccessor.HttpContext;
                viewContext.ViewData = new ViewDataDictionary<TModel>(new EmptyModelMetadataProvider(), new ModelStateDictionary())
                { Model = model };
                viewContext.Writer = output;

                view.RenderAsync(viewContext).GetAwaiter().GetResult();

                return output.ToString();
            }
        }
    }
}

Example usage:

using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using LibraryApi.Services;
using System.Dynamic;

namespace LibraryApi.Controllers
{
    [Route("api/[controller]")]
    public class ValuesController : Controller
    {
        ILogger<ValuesController> _logger;
        ViewRenderService _viewRender;
        public ValuesController(ILogger<ValuesController> logger, ViewRenderService viewRender)
        {
            _logger = logger;
            _viewRender = viewRender;
        }

        // GET api/values
        [HttpGet]
        public string Get()
        {
            //ViewModel is of type dynamic - just for testing
            dynamic x = new ExpandoObject();
            x.Test = "Yes";
            var viewWithViewModel = _viewRender.Render("eNotify/Confirm.cshtml", x);
            var viewWithoutViewModel = _viewRender.Render("MyFeature/Test.cshtml");
            return viewWithViewModel + viewWithoutViewModel;
        }
    }
}

Solution 2:^[2]

In the past, I’ve used the RazorEngine inside a Class Library because my goal was to render templates from within this Class Library.

From my understanding, you seem to be inside an MVC 6.0 project so why not use a RenderPartialViewToString() method without having to add the dependency on the RazorEngine?

Keep in mind, I'm only asking because I'm curious.

For example purposes, from within VS2015, I created a new ASP.NET Web Application and selected the Web Application template from the ASP.NET 5 Preview Templates.

Inside the ViewModels folder, I created a PersonViewModel:

public class PersonViewModel
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string FullName
    {
        get
        {
            return string.Format("{0} {1}", this.FirstName, this.LastName);
        }
    } 
}

I then created a new BaseController and added a RenderPartialViewToString() method:

public string RenderPartialViewToString(string viewName, object model)
{
    if (string.IsNullOrEmpty(viewName))
        viewName = ActionContext.ActionDescriptor.Name;

    ViewData.Model = model;

    using (StringWriter sw = new StringWriter())
    {
        var engine = Resolver.GetService(typeof(ICompositeViewEngine)) as ICompositeViewEngine;
        ViewEngineResult viewResult = engine.FindPartialView(ActionContext, viewName);

        ViewContext viewContext = new ViewContext(ActionContext, viewResult.View, ViewData, TempData, sw,new HtmlHelperOptions());

        var t = viewResult.View.RenderAsync(viewContext);
        t.Wait();

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

Credit goes to @DavidG for his method

Inside the Views-->Shared folder, I created a new Templates folder in which I’ve added a simple RegistrationTemplate.cshtml View strongly typed to my PersonViewModel like so:

@model MyWebProject.ViewModels.PersonViewModel
<!DOCTYPE html>
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="utf-8" />
    <title>Registration</title>
</head>
<body>
    <p>
        Hello, @Model.FullName
    </p>
</body>
</html>

The last step is to make my Controller inherit from my BaseController

public class MyController : BaseController

And create something like:

public IActionResult Index()
{
    var model = new PersonViewModel();
    model.FirstName = "Frank";
    model.LastName = "Underwood";
    var emailbody = base.RenderPartialViewToString("Templates/RegistrationTemplate", model);

    return View();
}

Of course, the example above is useless since I do nothing with the variable emailbody but the idea is to show how it’s used.

At this point, I could've(for example), invoke an EmailService and pass the emailbody:

_emailService.SendEmailAsync("[email protected]", "registration", emailbody);

I'm not sure if this is suitable alternative for your current task.

Solution 3:^[3]

Today I've finished with my library that can solve your problem. You can use it out of ASP.NET as it has no dependencies on it

Example:

string content = "Hello @Model.Name. Welcome to @Model.Title repository";

var model = new
{
  Name = "John Doe",
  Title = "RazorLight"
};

var engine = new RazorLightEngine();
string result = engine.ParseString(content, model);

//Output: Hello John Doe, Welcome to RazorLight repository

More: https://github.com/toddams/RazorLight

Solution 4:^[4]

To improve on @vlince answer (that wasn't working out of the box for me), here is what I did :

1- Create a base controller that your other controller will inherit

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

namespace YourNameSpace
{
    public class BaseController : Controller
    {
        protected ICompositeViewEngine viewEngine;

        public BaseController(ICompositeViewEngine viewEngine)
        {
            this.viewEngine = viewEngine;
        }

        protected string RenderViewAsString(object model, string viewName = null)
        {
            viewName = viewName ?? ControllerContext.ActionDescriptor.ActionName;
            ViewData.Model = model;

            using (StringWriter sw = new StringWriter())
            {
                IView view = viewEngine.FindView(ControllerContext, viewName, true).View;
                ViewContext viewContext = new ViewContext(ControllerContext, view, ViewData, TempData, sw, new HtmlHelperOptions());

                view.RenderAsync(viewContext).Wait();

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

2- Inherit the base controller and call the method

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.ViewEngines;

namespace YourNameSpace
{
    public class YourController : BaseController
    {
        public YourController(ICompositeViewEngine viewEngine) : base(viewEngine) { }

        public string Index(int? id)
        {
            var model = new MyModel { Name = "My Name" };

            return RenderViewAsString(model);
        }
    }
}

Solution 5:^[5]

ResolveUrlMethodName was removed. Therefore in your CreateHost here you're trying to set a property that doesn't exist :).

We decided to move ~/ handling from core Razor into a TagHelper implemented in the Microsoft.AspNet.Mvc.Razor assembly. Here's the commit to the bits that removed the method.

Hopefully this helps.

Solution 6:^[6]

Extension method for converting partial views to string response.

public static class PartialViewToString
{
    public static async Task<string> ToString(this PartialViewResult partialView, ActionContext actionContext)
    {
        using(var writer = new StringWriter())
        {
            var services = actionContext.HttpContext.RequestServices;
            var executor = services.GetRequiredService<PartialViewResultExecutor>();
            var view = executor.FindView(actionContext, partialView).View;
            var viewContext = new ViewContext(actionContext, view, partialView.ViewData, partialView.TempData, writer, new HtmlHelperOptions());
            await view.RenderAsync(viewContext);
            return writer.ToString();
        }
    }
}

Usage in your controller actions.

public async Task<IActionResult> Index()
{
    return await PartialView().ToString(ControllerContext)
}

.NET 5 Implementation

public static async Task<string> ViewToString(this PartialViewResult partialView, Controller controller)
    {
        using (var writer = new StringWriter())
        {
            var services = controller.ControllerContext.HttpContext.RequestServices;
            var viewEngine = services.GetService(typeof(ICompositeViewEngine)) as ICompositeViewEngine;
            var viewName = partialView.ViewName ?? controller.ControllerContext.ActionDescriptor.ActionName;
            var view = viewEngine.FindView(controller.ControllerContext, viewName, false).View;
            var viewContext = new ViewContext(controller.ControllerContext, view, partialView.ViewData, partialView.TempData, writer, new HtmlHelperOptions());
            await view.RenderAsync(viewContext);
            return writer.ToString();
        }
    }

Solution 7:^[7]

An alternative solution using just ASP.NET Core, no external libraries, and no reflection can be found here: https://weblogs.asp.net/ricardoperes/getting-html-for-a-viewresult-in-asp-net-core. It just requires a ViewResult and an HttpContext.

The idea is to pick up a ViewResult and call some method, say, ToHtml, to get the rendered output. This method can look like this:

public static class ViewResultExtensions {
    public static string ToHtml(this ViewResult result, HttpContext httpContext) {            
        var feature = httpContext.Features.Get<IRoutingFeature>();
        var routeData = feature.RouteData;
        var viewName = result.ViewName ?? routeData.Values["action"] as string;
        var actionContext = new ActionContext(httpContext, routeData, new ControllerActionDescriptor());
        var options = httpContext.RequestServices.GetRequiredService<IOptions<MvcViewOptions>>();
        var htmlHelperOptions = options.Value.HtmlHelperOptions;
        var viewEngineResult = result.ViewEngine?.FindView(actionContext, viewName, true) ?? options.Value.ViewEngines.Select(x => x.FindView(actionContext, viewName, true)).FirstOrDefault(x => x != null);
        var view = viewEngineResult.View;
        var builder = new StringBuilder();

        using (var output = new StringWriter(builder)) {
            var viewContext = new ViewContext(actionContext, view, result.ViewData, result.TempData, output, htmlHelperOptions);

            view
                .RenderAsync(viewContext)
                .GetAwaiter()
                .GetResult();
        }
        return builder.ToString();
    }
}

To use it, just do:

var view = this.View(“ViewName”);
var html = view.ToHtml();

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	Philip Holly
Solution 2	Community
Solution 3
Solution 4
Solution 5
Solution 6
Solution 7	karel

'Render Razor View to string in ASP.NET Core

Solution 1:[1]

Solution 2:[2]

Solution 3:[3]

Solution 4:[4]

Solution 5:[5]

Solution 6:[6]

Solution 7:[7]