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How to render Razor Page with a model in .Net Core app and send it with HttpClient

I'm working on Service which is generating dynamic Razor page connected with model, and the page needs to be sent to another service through HttpClient .
This is the ActionResult which is generating the view:
// GET: /Details/
public async Task<IActionResult> DetailsSend(int id)
{
if (id == null)
{
return NotFound();
}
var details = await _context.Details
.FirstOrDefaultAsync(d=> d.Id == id);
return View(details);
}
But i don't want to return this View(details). I want to send this dynamic view via httpclient. Any suggestion?

You could render the view as string like below:
public class EmployeesController : Controller
{
private readonly YourDbContext _context;
private readonly Microsoft.AspNetCore.Mvc.ViewEngines.ICompositeViewEngine _viewEngine;
public EmployeesController(ICompositeViewEngine viewEngine, YourDbContext context)
{
_viewEngine = viewEngine;
_context = context;
}
public async Task<string> DetailsSend(int id)
{
var details = await _context.Details
.FirstOrDefaultAsync(d => d.Id == id);
string view = "";
ViewData.Model = details;
using (var writer = new StringWriter())
{
ViewEngineResult viewResult = _viewEngine.FindView(ControllerContext, "Details", false);
ViewContext viewContext = new ViewContext(
ControllerContext,
viewResult.View,
ViewData,
TempData,
writer,
new HtmlHelperOptions()
);
await viewResult.View.RenderAsync(viewContext);
view = writer.GetStringBuilder().ToString();
}
return view;
}
}
Then you could use HttpClient to call this api and get the result like below:
public async Task<IActionResult> Index()
{
var url = "https://localhost:portNumber/ControllerName/detailssend/1";//it should be the url of your api
var httpClient = new HttpClient();
var response = await httpClient.GetAsync(url);
using (var content = response.Content)
{
//get the json result from your api
var result = await content.ReadAsStringAsync();
}
}

You should write as follows:
var details = (await context (d => d.Id == id)).Details.FirstOrDefaultAsync();

.NET Core 2.1 - Execute ControllerB.Action from ControllerA.Action returning a String

I have a system that generates emails. The content of parts of these emails is derived from ParialViews.
In my EmailController I want to be able to obtain the HTML snippet(s) that form areas of the email template by calling their relevant actions and inserting the View HTML.
I've seen the post(s) here (Return View as String in .NET Core) regarding it but it doesn't quite work...
The solution below does find and attempt to get the View HTML but it doesn't actually attempt to execute the View's controller action.
As the View is dynamic this results in an error.
So, can I execute ControllerB.Action retruning it's result as a string from within ControllerA.Action?
My current attempt:
The Service:
public interface IViewRenderService
{
Task<string> RenderToStringAsync(string viewName, object model);
}
public class ViewRenderService : IViewRenderService
{
private readonly IRazorViewEngine _razorViewEngine;
private readonly ITempDataProvider _tempDataProvider;
private readonly IServiceProvider _serviceProvider;
public ViewRenderService(IRazorViewEngine razorViewEngine,
ITempDataProvider tempDataProvider,
IServiceProvider serviceProvider)
{
_razorViewEngine = razorViewEngine;
_tempDataProvider = tempDataProvider;
_serviceProvider = serviceProvider;
}
public async Task<string> RenderToStringAsync(string viewName, object model)
{
var httpContext = new DefaultHttpContext { RequestServices = _serviceProvider };
var actionContext = new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
using (var sw = new StringWriter())
{
var viewResult = _razorViewEngine.FindView(actionContext, viewName, false);
if (viewResult.View == null)
{
throw new ArgumentNullException($"{viewName} does not match any available view");
}
var viewDictionary = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary())
{
Model = model
};
var viewContext = new ViewContext(
actionContext,
viewResult.View,
viewDictionary,
new TempDataDictionary(actionContext.HttpContext, _tempDataProvider),
sw,
new HtmlHelperOptions()
);
await viewResult.View.RenderAsync(viewContext);
return sw.ToString();
}
}
}
Starup.cs
services.AddScoped<IViewRenderService, ViewRenderService>();
Controller A
private readonly IViewRenderService _viewRenderService;
public ReportController(...
IViewRenderService viewRenderService)
{
...
_viewRenderService = viewRenderService;
}
The call from Controller A:
var theHtmlString = await _viewRenderService.RenderToStringAsync("ControllerB/Action1", new { parameters = paramsmodel });

Render a Razor Page to string

Problem:
I need to render a Razor Page partial to a string.
Why I want this:
I want to create a controller action that responds with JSON containing a partial view and other optional parameters.
Attempts:
I am familiar with the following example that renders a View to a string: https://github.com/aspnet/Entropy/blob/dev/samples/Mvc.RenderViewToString/RazorViewToStringRenderer.cs
However, it is not compatible with Pages, as it only searches in the Views directory, so even if I give it an absolute path to the partial it tries to locate my _Layout.cshtml (which it shouldn't even do!) and fails to find it.
I have tried to modify it so it renders pages, but I end up getting a NullReferenceException for ViewData in my partial when attempting to render it. I suspect it has to do with NullView, but I have no idea what to put there instead (the constructor for RazorView requires many objects that I don't know how to get correctly).
The code:
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0: https://www.apache.org/licenses/LICENSE-2.0
// Modified by OronDF343: Uses pages instead of views.
using System;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Abstractions;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Mvc.ViewFeatures.Internal;
using Microsoft.AspNetCore.Routing;
namespace TestAspNetCore.Services
{
public class RazorPageToStringRenderer
{
private readonly IRazorViewEngine _viewEngine;
private readonly ITempDataProvider _tempDataProvider;
private readonly IServiceProvider _serviceProvider;
public RazorPageToStringRenderer(
IRazorViewEngine viewEngine,
ITempDataProvider tempDataProvider,
IServiceProvider serviceProvider)
{
_viewEngine = viewEngine;
_tempDataProvider = tempDataProvider;
_serviceProvider = serviceProvider;
}
public async Task<string> RenderPageToStringAsync<TModel>(string viewName, TModel model)
{
var actionContext = GetActionContext();
var page = FindPage(actionContext, viewName);
using (var output = new StringWriter())
{
var viewContext = new ViewContext(actionContext,
new NullView(),
new ViewDataDictionary<TModel>(new EmptyModelMetadataProvider(),
new ModelStateDictionary())
{
Model = model
},
new TempDataDictionary(actionContext.HttpContext,
_tempDataProvider),
output,
new HtmlHelperOptions());
page.ViewContext = viewContext;
await page.ExecuteAsync();
return output.ToString();
}
}
private IRazorPage FindPage(ActionContext actionContext, string pageName)
{
var getPageResult = _viewEngine.GetPage(executingFilePath: null, pagePath: pageName);
if (getPageResult.Page != null)
{
return getPageResult.Page;
}
var findPageResult = _viewEngine.FindPage(actionContext, pageName);
if (findPageResult.Page != null)
{
return findPageResult.Page;
}
var searchedLocations = getPageResult.SearchedLocations.Concat(findPageResult.SearchedLocations);
var errorMessage = string.Join(
Environment.NewLine,
new[] { $"Unable to find page '{pageName}'. The following locations were searched:" }.Concat(searchedLocations));
throw new InvalidOperationException(errorMessage);
}
private ActionContext GetActionContext()
{
var httpContext = new DefaultHttpContext { RequestServices = _serviceProvider };
return new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
}
}
}

This is how I did it.
As always register the Service in Startup.cs
services.AddScoped<IViewRenderService, ViewRenderService>();
The Service is defined as follows:
public interface IViewRenderService
{
Task<string> RenderToStringAsync<T>(string viewName, T model) where T : PageModel;
}
public class ViewRenderService : IViewRenderService
{
private readonly IRazorViewEngine _razorViewEngine;
private readonly ITempDataProvider _tempDataProvider;
private readonly IServiceProvider _serviceProvider;
private readonly IHttpContextAccessor _httpContext;
private readonly IActionContextAccessor _actionContext;
private readonly IRazorPageActivator _activator;
public ViewRenderService(IRazorViewEngine razorViewEngine,
ITempDataProvider tempDataProvider,
IServiceProvider serviceProvider,
IHttpContextAccessor httpContext,
IRazorPageActivator activator,
IActionContextAccessor actionContext)
{
_razorViewEngine = razorViewEngine;
_tempDataProvider = tempDataProvider;
_serviceProvider = serviceProvider;
_httpContext = httpContext;
_actionContext = actionContext;
_activator = activator;
}
public async Task<string> RenderToStringAsync<T>(string pageName, T model) where T : PageModel
{
var actionContext =
new ActionContext(
_httpContext.HttpContext,
_httpContext.HttpContext.GetRouteData(),
_actionContext.ActionContext.ActionDescriptor
);
using (var sw = new StringWriter())
{
var result = _razorViewEngine.FindPage(actionContext, pageName);
if (result.Page == null)
{
throw new ArgumentNullException($"The page {pageName} cannot be found.");
}
var view = new RazorView(_razorViewEngine,
_activator,
new List<IRazorPage>(),
result.Page,
HtmlEncoder.Default,
new DiagnosticListener("ViewRenderService"));
var viewContext = new ViewContext(
actionContext,
view,
new ViewDataDictionary<T>(new EmptyModelMetadataProvider(), new ModelStateDictionary())
{
Model = model
},
new TempDataDictionary(
_httpContext.HttpContext,
_tempDataProvider
),
sw,
new HtmlHelperOptions()
);
var page = ((Page)result.Page);
page.PageContext = new Microsoft.AspNetCore.Mvc.RazorPages.PageContext
{
ViewData = viewContext.ViewData
};
page.ViewContext = viewContext;
_activator.Activate(page, viewContext);
await page.ExecuteAsync();
return sw.ToString();
}
}
}
I call it like this
emailView.Body = await this._viewRenderService.RenderToStringAsync("Email/ConfirmAccount", new Email.ConfirmAccountModel
{
EmailView = emailView,
});
"Email/ConfirmAccount" is the path to my Razor page (Under pages). "ConfirmAccountModel" is my page model for that page.
ViewData is null because the ViewData for the Page is set when the PageContext is set, so if this is not set ViewData is null.
I also found that I had to call
_activator.Activate(page, viewContext);
For it all to work. This is not fully tested yet so may not work for all scenarios but should help you get started.

If like me you don't get GetRouteData() from _httpContext.HttpContext and _actionContext is null, you can create an extension:
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewEngines;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Text.Encodings.Web;
using System.Threading.Tasks;
namespace Utils
{
public static class PageExtensions
{
public static async Task<string> RenderViewAsync(this PageModel pageModel, string pageName)
{
var actionContext = new ActionContext(
pageModel.HttpContext,
pageModel.RouteData,
pageModel.PageContext.ActionDescriptor
);
using (var sw = new StringWriter())
{
IRazorViewEngine _razorViewEngine = pageModel.HttpContext.RequestServices.GetService(typeof(IRazorViewEngine)) as IRazorViewEngine;
IRazorPageActivator _activator = pageModel.HttpContext.RequestServices.GetService(typeof(IRazorPageActivator)) as IRazorPageActivator;
var result = _razorViewEngine.FindPage(actionContext, pageName);
if (result.Page == null)
{
throw new ArgumentNullException($"The page {pageName} cannot be found.");
}
var page = result.Page;
var view = new RazorView(_razorViewEngine,
_activator,
new List<IRazorPage>(),
page,
HtmlEncoder.Default,
new DiagnosticListener("ViewRenderService"));
var viewContext = new ViewContext(
actionContext,
view,
pageModel.ViewData,
pageModel.TempData,
sw,
new HtmlHelperOptions()
);
var pageNormal = ((Page)result.Page);
pageNormal.PageContext = pageModel.PageContext;
pageNormal.ViewContext = viewContext;
_activator.Activate(pageNormal, viewContext);
await page.ExecuteAsync();
return sw.ToString();
}
}
}
}
Note: this code only render the page being called and omit the layout.
You just have to call it from your PageModel like this:
var s = this.RenderViewAsync("sendEmail").Result;
"sendEmail" is the name of your PageModel view and the path is /Pages/sendEmail.cshtml

Here is the route I have gone down. Very simple and works a treat...
using System;
using System.IO;
using System.Net;
namespace gMIS.Rendering
{
public static class RazorPage
{
public static string RenderToString(string url)
{
try
{
//Grab page
WebRequest request = WebRequest.Create(url);
WebResponse response = request.GetResponse();
Stream data = response.GetResponseStream();
string html = String.Empty;
using (StreamReader sr = new StreamReader(data))
{
html = sr.ReadToEnd();
}
return html;
}
catch (Exception err)
{
return {Handle as you see fit};
}
}
}
}
Called as such....
var msg = RazorPage.RenderToString(url);
Example:
var pathToRazorPageFolder = request.PathToRazorPageFolder();
var msg = RazorPage.RenderToString($"{pathToRazorPageFolder}/Task_Summary?userGuid={userGuid}&taskId={task.Task_ID}&includelink=true&linkuserGuid={linkUserGuid}");
Above example uses this extension I created to help get the base path of my app.
namespace Microsoft.AspNetCore.Http
{
public static class RequestExtension
{
public static string PathToRazorPageFolder(this HttpRequest request)
{
if (request != null) {
var requestPath = request.Path.ToString();
var returnPathToFolder = request.Scheme + "://" + request.Host + requestPath.Substring(0, requestPath.LastIndexOf("/")); ;
return returnPathToFolder;
} else
{
return "HttpRequest was null";
}
}
}
}
I know that this doesn't use Dependency Injection, but man it's simple. And it just works. And works with any page no matter how it is hosted. Be that page be within or even outside your application.

I had the same problem.
I looked into the RazorViewEngine source code and found out that the page
is searched using the "page" route data:
var routeData = new RouteData();
routeData.Values.Add("page", "/Folder/MyPage");
It's working for me with the full path "/Folder/MyPage" in the routeData, and the page name "MyPage" in the GetPage call.

Pre-compiled Razor view to string with ASP.NET Core

How is it possible to render a Razor view to a string, while using the new Razor pre-compilation from ASP.NET Core 1.1?
The following code is from the example and the exception will be thrown because viewResult.View is null.
var httpContext = new DefaultHttpContext { RequestServices = _serviceProvider };
var actionContext = new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
var viewResult = _razorViewEngine.FindView(actionContext, viewName, false);
if (viewResult.View == null)
{
throw new ArgumentNullException($"{viewName} does not match any available view");
}
https://blogs.msdn.microsoft.com/webdev/2016/10/25/announcing-asp-net-core-1-1-preview-1/
Old way (example): File -> Razor -> Compile -> string

It should already work. When you call:
viewResult.View.RenderAsync(viewContext);
It will find the pre-compiled view and use that one rather than compiling the view again.

You have to implement an IViewRenderService and register is in your Startup.cs. Then add a function like this:
public class ViewRenderService : IViewRenderService
{
private readonly ITempDataProvider _tempDataProvider;
private readonly IServiceProvider _serviceProvider;
private readonly HttpContext _context;
private readonly ICompositeViewEngine _viewEngine;
private const string ControllerStr = "controller";
public ViewRenderService(
ITempDataProvider tempDataProvider,
IServiceProvider serviceProvider,
IHttpContextAccessor accessor,
ICompositeViewEngine viewEngine)
{
_tempDataProvider = tempDataProvider;
_serviceProvider = serviceProvider;
_context = accessor.HttpContext;
_viewEngine = viewEngine;
}
public async Task<string> RenderToStringAsync(string viewName, object model)
{
return await RenderToStringAsync(viewName, model, null);
}
public async Task<string> RenderToStringAsync(string viewName, object model, ViewDataDictionary viewDataDictionary)
{
var controller = string.Empty;
viewName = viewName?.TrimStart(new char[] { '/' });
Regex rex = new Regex(#"^(\w+)\/(.*)$");
Match match = rex.Match(viewName);
if (match.Success)
{
controller = match.Groups[1].Value;
viewName = match.Groups[2].Value;
}
var routeData = new RouteData();
routeData.Values.Add(ControllerStr, controller);
var actionContext = new ActionContext(_context, routeData, new ActionDescriptor());
var viewResult = _viewEngine.FindView(actionContext, viewName, false);
if (viewResult.View == null)
{
Console.WriteLine($"Searched the following locations: {string.Join(", ", viewResult.SearchedLocations)} for folder \"{controller}\" and view \"{viewName}\"");
throw new ArgumentNullException($"{viewName} does not match any available view");
}
var viewDictionary = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary())
{
Model = model
};
if (viewDataDictionary != null)
{
foreach (var obj in viewDataDictionary)
{
viewDictionary.Add(obj);
}
}
using (var sw = new StringWriter())
{
var viewContext = new ViewContext(
actionContext,
viewResult.View,
viewDictionary,
new TempDataDictionary(_context, _tempDataProvider),
sw,
new HtmlHelperOptions()
);
viewContext.RouteData = _context.GetRouteData();
await viewResult.View.RenderAsync(viewContext);
return sw.ToString();
}
}
}

Output buffering in ASP.NET MVC [duplicate]

I want to output two different views (one as a string that will be sent as an email), and the other the page displayed to a user.
Is this possible in ASP.NET MVC beta?
I've tried multiple examples:
1. RenderPartial to String in ASP.NET MVC Beta
If I use this example, I receive the "Cannot redirect after HTTP
headers have been sent.".
2. MVC Framework: Capturing the output of a view
If I use this, I seem to be unable to do a redirectToAction, as it
tries to render a view that may not exist. If I do return the view, it
is completely messed up and doesn't look right at all.
Does anyone have any ideas/solutions to these issues i have, or have any suggestions for better ones?
Many thanks!
Below is an example. What I'm trying to do is create the GetViewForEmail method:
public ActionResult OrderResult(string ref)
{
//Get the order
Order order = OrderService.GetOrder(ref);
//The email helper would do the meat and veg by getting the view as a string
//Pass the control name (OrderResultEmail) and the model (order)
string emailView = GetViewForEmail("OrderResultEmail", order);
//Email the order out
EmailHelper(order, emailView);
return View("OrderResult", order);
}
Accepted answer from Tim Scott (changed and formatted a little by me):
public virtual string RenderViewToString(
ControllerContext controllerContext,
string viewPath,
string masterPath,
ViewDataDictionary viewData,
TempDataDictionary tempData)
{
Stream filter = null;
ViewPage viewPage = new ViewPage();
//Right, create our view
viewPage.ViewContext = new ViewContext(controllerContext, new WebFormView(viewPath, masterPath), viewData, tempData);
//Get the response context, flush it and get the response filter.
var response = viewPage.ViewContext.HttpContext.Response;
response.Flush();
var oldFilter = response.Filter;
try
{
//Put a new filter into the response
filter = new MemoryStream();
response.Filter = filter;
//Now render the view into the memorystream and flush the response
viewPage.ViewContext.View.Render(viewPage.ViewContext, viewPage.ViewContext.HttpContext.Response.Output);
response.Flush();
//Now read the rendered view.
filter.Position = 0;
var reader = new StreamReader(filter, response.ContentEncoding);
return reader.ReadToEnd();
}
finally
{
//Clean up.
if (filter != null)
{
filter.Dispose();
}
//Now replace the response filter
response.Filter = oldFilter;
}
}
Example usage
Assuming a call from the controller to get the order confirmation email, passing the Site.Master location.
string myString = RenderViewToString(this.ControllerContext, "~/Views/Order/OrderResultEmail.aspx", "~/Views/Shared/Site.Master", this.ViewData, this.TempData);

Here's what I came up with, and it's working for me. I added the following method(s) to my controller base class. (You can always make these static methods somewhere else that accept a controller as a parameter I suppose)
MVC2 .ascx style
protected string RenderViewToString<T>(string viewPath, T model) {
ViewData.Model = model;
using (var writer = new StringWriter()) {
var view = new WebFormView(ControllerContext, viewPath);
var vdd = new ViewDataDictionary<T>(model);
var viewCxt = new ViewContext(ControllerContext, view, vdd,
new TempDataDictionary(), writer);
viewCxt.View.Render(viewCxt, writer);
return writer.ToString();
}
}
Razor .cshtml style
public string RenderRazorViewToString(string viewName, object model)
{
ViewData.Model = model;
using (var sw = new StringWriter())
{
var viewResult = ViewEngines.Engines.FindPartialView(ControllerContext,
viewName);
var viewContext = new ViewContext(ControllerContext, viewResult.View,
ViewData, TempData, sw);
viewResult.View.Render(viewContext, sw);
viewResult.ViewEngine.ReleaseView(ControllerContext, viewResult.View);
return sw.GetStringBuilder().ToString();
}
}
Edit: added Razor code.

This answer is not on my way . This is originally from https://stackoverflow.com/a/2759898/2318354 but here I have show the way to use it with "Static" Keyword to make it common for all Controllers .
For that you have to make static class in class file . (Suppose your Class File Name is Utils.cs )
This example is For Razor.
Utils.cs
public static class RazorViewToString
{
public static string RenderRazorViewToString(this Controller controller, string viewName, object model)
{
controller.ViewData.Model = model;
using (var sw = new StringWriter())
{
var viewResult = ViewEngines.Engines.FindPartialView(controller.ControllerContext, viewName);
var viewContext = new ViewContext(controller.ControllerContext, viewResult.View, controller.ViewData, controller.TempData, sw);
viewResult.View.Render(viewContext, sw);
viewResult.ViewEngine.ReleaseView(controller.ControllerContext, viewResult.View);
return sw.GetStringBuilder().ToString();
}
}
}
Now you can call this class from your controller by adding NameSpace in your Controller File as following way by passing "this" as parameter to Controller.
string result = RazorViewToString.RenderRazorViewToString(this ,"ViewName", model);
As suggestion given by #Sergey this extension method can also call from cotroller as given below
string result = this.RenderRazorViewToString("ViewName", model);
I hope this will be useful to you make code clean and neat.

This works for me:
public virtual string RenderView(ViewContext viewContext)
{
var response = viewContext.HttpContext.Response;
response.Flush();
var oldFilter = response.Filter;
Stream filter = null;
try
{
filter = new MemoryStream();
response.Filter = filter;
viewContext.View.Render(viewContext, viewContext.HttpContext.Response.Output);
response.Flush();
filter.Position = 0;
var reader = new StreamReader(filter, response.ContentEncoding);
return reader.ReadToEnd();
}
finally
{
if (filter != null)
{
filter.Dispose();
}
response.Filter = oldFilter;
}
}

I found a new solution that renders a view to string without having to mess with the Response stream of the current HttpContext (which doesn't allow you to change the response's ContentType or other headers).
Basically, all you do is create a fake HttpContext for the view to render itself:
/// <summary>Renders a view to string.</summary>
public static string RenderViewToString(this Controller controller,
string viewName, object viewData) {
//Create memory writer
var sb = new StringBuilder();
var memWriter = new StringWriter(sb);
//Create fake http context to render the view
var fakeResponse = new HttpResponse(memWriter);
var fakeContext = new HttpContext(HttpContext.Current.Request, fakeResponse);
var fakeControllerContext = new ControllerContext(
new HttpContextWrapper(fakeContext),
controller.ControllerContext.RouteData,
controller.ControllerContext.Controller);
var oldContext = HttpContext.Current;
HttpContext.Current = fakeContext;
//Use HtmlHelper to render partial view to fake context
var html = new HtmlHelper(new ViewContext(fakeControllerContext,
new FakeView(), new ViewDataDictionary(), new TempDataDictionary()),
new ViewPage());
html.RenderPartial(viewName, viewData);
//Restore context
HttpContext.Current = oldContext;
//Flush memory and return output
memWriter.Flush();
return sb.ToString();
}
/// <summary>Fake IView implementation used to instantiate an HtmlHelper.</summary>
public class FakeView : IView {
#region IView Members
public void Render(ViewContext viewContext, System.IO.TextWriter writer) {
throw new NotImplementedException();
}
#endregion
}
This works on ASP.NET MVC 1.0, together with ContentResult, JsonResult, etc. (changing Headers on the original HttpResponse doesn't throw the "Server cannot set content type after HTTP headers have been sent" exception).
Update: in ASP.NET MVC 2.0 RC, the code changes a bit because we have to pass in the StringWriter used to write the view into the ViewContext:
//...
//Use HtmlHelper to render partial view to fake context
var html = new HtmlHelper(
new ViewContext(fakeControllerContext, new FakeView(),
new ViewDataDictionary(), new TempDataDictionary(), memWriter),
new ViewPage());
html.RenderPartial(viewName, viewData);
//...

This article describes how to render a View to a string in different scenarios:
MVC Controller calling another of its own ActionMethods
MVC Controller calling an ActionMethod of another MVC Controller
WebAPI Controller calling an ActionMethod of an MVC Controller
The solution/code is provided as a class called ViewRenderer. It is part of Rick Stahl's WestwindToolkit at GitHub.
Usage (3. - WebAPI example):
string html = ViewRenderer.RenderView("~/Areas/ReportDetail/Views/ReportDetail/Index.cshtml", ReportVM.Create(id));

If you want to forgo MVC entirely, thereby avoiding all the HttpContext mess...
using RazorEngine;
using RazorEngine.Templating; // For extension methods.
string razorText = System.IO.File.ReadAllText(razorTemplateFileLocation);
string emailBody = Engine.Razor.RunCompile(razorText, "templateKey", typeof(Model), model);
This uses the awesome open source Razor Engine here:
https://github.com/Antaris/RazorEngine

Additional tip for ASP NET CORE:
Interface:
public interface IViewRenderer
{
Task<string> RenderAsync<TModel>(Controller controller, string name, TModel model);
}
Implementation:
public class ViewRenderer : IViewRenderer
{
private readonly IRazorViewEngine viewEngine;
public ViewRenderer(IRazorViewEngine viewEngine) => this.viewEngine = viewEngine;
public async Task<string> RenderAsync<TModel>(Controller controller, string name, TModel model)
{
ViewEngineResult viewEngineResult = this.viewEngine.FindView(controller.ControllerContext, name, false);
if (!viewEngineResult.Success)
{
throw new InvalidOperationException(string.Format("Could not find view: {0}", name));
}
IView view = viewEngineResult.View;
controller.ViewData.Model = model;
await using var writer = new StringWriter();
var viewContext = new ViewContext(
controller.ControllerContext,
view,
controller.ViewData,
controller.TempData,
writer,
new HtmlHelperOptions());
await view.RenderAsync(viewContext);
return writer.ToString();
}
}
Registration in Startup.cs
...
services.AddSingleton<IViewRenderer, ViewRenderer>();
...
And usage in controller:
public MyController: Controller
{
private readonly IViewRenderer renderer;
public MyController(IViewRendere renderer) => this.renderer = renderer;
public async Task<IActionResult> MyViewTest
{
var view = await this.renderer.RenderAsync(this, "MyView", model);
return new OkObjectResult(view);
}
}

To render a view to a string in the Service Layer without having to pass ControllerContext around, there is a good Rick Strahl article here http://www.codemag.com/Article/1312081 that creates a generic controller. Code summary below:
// Some Static Class
public static string RenderViewToString(ControllerContext context, string viewPath, object model = null, bool partial = false)
{
// first find the ViewEngine for this view
ViewEngineResult viewEngineResult = null;
if (partial)
viewEngineResult = ViewEngines.Engines.FindPartialView(context, viewPath);
else
viewEngineResult = ViewEngines.Engines.FindView(context, viewPath, null);
if (viewEngineResult == null)
throw new FileNotFoundException("View cannot be found.");
// get the view and attach the model to view data
var view = viewEngineResult.View;
context.Controller.ViewData.Model = model;
string result = null;
using (var sw = new StringWriter())
{
var ctx = new ViewContext(context, view, context.Controller.ViewData, context.Controller.TempData, sw);
view.Render(ctx, sw);
result = sw.ToString();
}
return result;
}
// In the Service Class
public class GenericController : Controller
{ }
public static T CreateController<T>(RouteData routeData = null) where T : Controller, new()
{
// create a disconnected controller instance
T controller = new T();
// get context wrapper from HttpContext if available
HttpContextBase wrapper;
if (System.Web.HttpContext.Current != null)
wrapper = new HttpContextWrapper(System.Web.HttpContext.Current);
else
throw new InvalidOperationException("Cannot create Controller Context if no active HttpContext instance is available.");
if (routeData == null)
routeData = new RouteData();
// add the controller routing if not existing
if (!routeData.Values.ContainsKey("controller") &&
!routeData.Values.ContainsKey("Controller"))
routeData.Values.Add("controller", controller.GetType().Name.ToLower().Replace("controller", ""));
controller.ControllerContext = new ControllerContext(wrapper, routeData, controller);
return controller;
}
Then to render the View in the Service class:
var stringView = RenderViewToString(CreateController<GenericController>().ControllerContext, "~/Path/To/View/Location/_viewName.cshtml", theViewModel, true);

you can get the view in string using this way
protected string RenderPartialViewToString(string viewName, object model)
{
if (string.IsNullOrEmpty(viewName))
viewName = ControllerContext.RouteData.GetRequiredString("action");
if (model != null)
ViewData.Model = model;
using (StringWriter sw = new StringWriter())
{
ViewEngineResult viewResult = ViewEngines.Engines.FindPartialView(ControllerContext, viewName);
ViewContext viewContext = new ViewContext(ControllerContext, viewResult.View, ViewData, TempData, sw);
viewResult.View.Render(viewContext, sw);
return sw.GetStringBuilder().ToString();
}
}
We can call this method in two way
string strView = RenderPartialViewToString("~/Views/Shared/_Header.cshtml", null)
OR
var model = new Person()
string strView = RenderPartialViewToString("~/Views/Shared/_Header.cshtml", model)

I am using MVC 1.0 RTM and none of the above solutions worked for me. But this one did:
Public Function RenderView(ByVal viewContext As ViewContext) As String
Dim html As String = ""
Dim response As HttpResponse = HttpContext.Current.Response
Using tempWriter As New System.IO.StringWriter()
Dim privateMethod As MethodInfo = response.GetType().GetMethod("SwitchWriter", BindingFlags.NonPublic Or BindingFlags.Instance)
Dim currentWriter As Object = privateMethod.Invoke(response, BindingFlags.NonPublic Or BindingFlags.Instance Or BindingFlags.InvokeMethod, Nothing, New Object() {tempWriter}, Nothing)
Try
viewContext.View.Render(viewContext, Nothing)
html = tempWriter.ToString()
Finally
privateMethod.Invoke(response, BindingFlags.NonPublic Or BindingFlags.Instance Or BindingFlags.InvokeMethod, Nothing, New Object() {currentWriter}, Nothing)
End Try
End Using
Return html
End Function

I saw an implementation for MVC 3 and Razor from another website, it worked for me:
public static string RazorRender(Controller context, string DefaultAction)
{
string Cache = string.Empty;
System.Text.StringBuilder sb = new System.Text.StringBuilder();
System.IO.TextWriter tw = new System.IO.StringWriter(sb);
RazorView view_ = new RazorView(context.ControllerContext, DefaultAction, null, false, null);
view_.Render(new ViewContext(context.ControllerContext, view_, new ViewDataDictionary(), new TempDataDictionary(), tw), tw);
Cache = sb.ToString();
return Cache;
}
public static string RenderRazorViewToString(string viewName, object model)
{
ViewData.Model = model;
using (var sw = new StringWriter())
{
var viewResult = ViewEngines.Engines.FindPartialView(ControllerContext, viewName);
var viewContext = new ViewContext(ControllerContext, viewResult.View, ViewData, TempData, sw);
viewResult.View.Render(viewContext, sw);
return sw.GetStringBuilder().ToString();
}
}
public static class HtmlHelperExtensions
{
public static string RenderPartialToString(ControllerContext context, string partialViewName, ViewDataDictionary viewData, TempDataDictionary tempData)
{
ViewEngineResult result = ViewEngines.Engines.FindPartialView(context, partialViewName);
if (result.View != null)
{
StringBuilder sb = new StringBuilder();
using (StringWriter sw = new StringWriter(sb))
{
using (HtmlTextWriter output = new HtmlTextWriter(sw))
{
ViewContext viewContext = new ViewContext(context, result.View, viewData, tempData, output);
result.View.Render(viewContext, output);
}
}
return sb.ToString();
}
return String.Empty;
}
}
More on Razor render- MVC3 View Render to String

Quick tip
For a strongly typed Model just add it to the ViewData.Model property before passing to RenderViewToString. e.g
this.ViewData.Model = new OrderResultEmailViewModel(order);
string myString = RenderViewToString(this.ControllerContext, "~/Views/Order/OrderResultEmail.aspx", "~/Views/Shared/Site.Master", this.ViewData, this.TempData);

To repeat from a more unknown question, take a look at MvcIntegrationTestFramework.
It makes saves you writing your own helpers to stream result and is proven to work well enough. I'd assume this would be in a test project and as a bonus you would have the other testing capabilities once you've got this setup. Main bother would probably be sorting out the dependency chain.
private static readonly string mvcAppPath =
Path.GetFullPath(AppDomain.CurrentDomain.BaseDirectory
+ "\\..\\..\\..\\MyMvcApplication");
private readonly AppHost appHost = new AppHost(mvcAppPath);
[Test]
public void Root_Url_Renders_Index_View()
{
appHost.SimulateBrowsingSession(browsingSession => {
RequestResult result = browsingSession.ProcessRequest("");
Assert.IsTrue(result.ResponseText.Contains("<!DOCTYPE html"));
});
}

Here is a class I wrote to do this for ASP.NETCore RC2. I use it so I can generate html email using Razor.
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Abstractions;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewEngines;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Routing;
using System.IO;
using System.Threading.Tasks;
namespace cloudscribe.Web.Common.Razor
{
/// <summary>
/// the goal of this class is to provide an easy way to produce an html string using
/// Razor templates and models, for use in generating html email.
/// </summary>
public class ViewRenderer
{
public ViewRenderer(
ICompositeViewEngine viewEngine,
ITempDataProvider tempDataProvider,
IHttpContextAccessor contextAccesor)
{
this.viewEngine = viewEngine;
this.tempDataProvider = tempDataProvider;
this.contextAccesor = contextAccesor;
}
private ICompositeViewEngine viewEngine;
private ITempDataProvider tempDataProvider;
private IHttpContextAccessor contextAccesor;
public async Task<string> RenderViewAsString<TModel>(string viewName, TModel model)
{
var viewData = new ViewDataDictionary<TModel>(
metadataProvider: new EmptyModelMetadataProvider(),
modelState: new ModelStateDictionary())
{
Model = model
};
var actionContext = new ActionContext(contextAccesor.HttpContext, new RouteData(), new ActionDescriptor());
var tempData = new TempDataDictionary(contextAccesor.HttpContext, tempDataProvider);
using (StringWriter output = new StringWriter())
{
ViewEngineResult viewResult = viewEngine.FindView(actionContext, viewName, true);
ViewContext viewContext = new ViewContext(
actionContext,
viewResult.View,
viewData,
tempData,
output,
new HtmlHelperOptions()
);
await viewResult.View.RenderAsync(viewContext);
return output.GetStringBuilder().ToString();
}
}
}
}

I found a better way to render razor view page when I got error with the methods above, this solution for both web form environment and mvc environment.
No controller is needed.
Here is the code example, in this example I simulated a mvc action with an async http handler:
/// <summary>
/// Enables processing of HTTP Web requests asynchronously by a custom HttpHandler that implements the IHttpHandler interface.
/// </summary>
/// <param name="context">An HttpContext object that provides references to the intrinsic server objects.</param>
/// <returns>The task to complete the http request.</returns>
protected override async Task ProcessRequestAsync(HttpContext context)
{
if (this._view == null)
{
this.OnError(context, new FileNotFoundException("Can not find the mvc view file.".Localize()));
return;
}
object model = await this.LoadModelAsync(context);
WebPageBase page = WebPageBase.CreateInstanceFromVirtualPath(this._view.VirtualPath);
using (StringWriter sw = new StringWriter())
{
page.ExecutePageHierarchy(new WebPageContext(new HttpContextWrapper(context), page, model), sw);
await context.Response.Output.WriteAsync(sw.GetStringBuilder().ToString());
}
}

The easiest way for me was:
public string GetFileAsString(string path)
{
var html = "";
FileStream fileStream = new FileStream(path, FileMode.Open);
using (StreamReader reader = new StreamReader(fileStream))
{
html += reader.ReadLine();
}
return html;
}
I use this for emails and make sure that the file only contains CSS and HTML