ActionResult to String

ActionResult to String - c#

I know there are a lot of questions similar, but I didn't get the answer I wanted in any of them.
I want to convert, as it is, an ActionResult to String, by doing something like that:
public ActionResult ProductDetail(int id)
{
// ... lots of operations that include usage of ViewBag and a Model ...
return View(product);
}
To show the product page to the client, but also I want to be able to send it by JSON, like:
public JsonResult ProductDetailJSON(int id)
{
// ... lots of operations that include usage of ViewBag and a Model ...
return Json(new {
html = this.ProductDetail(id).ToString(),
name = ""
// ... more properties
}, JsonRequestBehavior.AllowGet);
}
So I will invoke the Controller Action and get its response (a ActionResult, that is actually a ViewResult) and turn it into a String, but having it created using all the business code of the controller method (including, specially, ViewBag usage).
EDIT Clarification about why I want to to do it that way
I need to be able to present the product in the browser, so I create my Controller Action called ProductDetail, and works perfectly fine.
After that comes the need to have an API that gives, for a given product a JSON object with some meta-data (like sold units, name, etc.) and the View. One option was to send a link to the view and that's all... but the view MUST be inlined as a client requirement.
To avoid code repetition and to keep it clean, I'd like to invoke the method ProductDetail, and capture the HTML Raw response to put it inside the JSON response as an String.
I've seen others rendering the View with methods like this one:
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();
}
}
But that way does not execute the controller logic.

Here is a working solution.
Create new classes:
public class ResponseCapture : IDisposable
{
private readonly HttpResponseBase response;
private readonly TextWriter originalWriter;
private StringWriter localWriter;
public ResponseCapture(HttpResponseBase response)
{
this.response = response;
originalWriter = response.Output;
localWriter = new StringWriter();
response.Output = localWriter;
}
public override string ToString()
{
localWriter.Flush();
return localWriter.ToString();
}
public void Dispose()
{
if (localWriter != null)
{
localWriter.Dispose();
localWriter = null;
response.Output = originalWriter;
}
}
}
public static class ActionResultExtensions
{
public static string Capture(this ActionResult result, ControllerContext controllerContext)
{
using (var it = new ResponseCapture(controllerContext.RequestContext.HttpContext.Response))
{
result.ExecuteResult(controllerContext);
return it.ToString();
}
}
}
in your json method do this:
public JsonResult ProductDetailJSON(int id)
{
// ... lots of operations that include usage of ViewBag and a Model ...
return Json(new {
// ControllerContext - modify it so it accepts Id
html = View("ProductDetail").Capture(ControllerContext),
name = ""
// ... more properties
}, JsonRequestBehavior.AllowGet);
}

Related

C# ASP.NET Is there an alternative to duplicating error checking on every controller action

If I have a controller with quite a few actions, doing similar things e.g. Gets data from an api, does something with it, returns view with updated model. Is there a better way to handle errors. Currently I do this on a number of action methods, obviously this duplication doesn't feel right but I can't think of an alternative. Thanks
public async Task<IActionResult> method(string id)
{
var result = await _flightRepository.GetLightById(id);
if (!result.Valid)
{
return View("ErrorPage", result.Error.Message);
}
var viewModel = new FlightViewModel
{
Flight = result.Result
};
return View(viewModel);
}
Basically I want to somehow encapsulate the error handling logic to return the error view if valid is false, otherwise populate viewmodel and return view. The valid property returns true if there is an error with the request (this is done in api layer)
Thanks for any help

You should use Filters to reuse code among your actions.
For example in your case your filter could be:
public class FlightValidator: ActionFilterAttribute
{
private readonly string _flightIdRouteKey; // e.g 23
private readonly string _errorViewName; // e.g "ErrorPage"
private readonly IFlightRepository _flightRepo;
public FlightValidator(string flightIdRouteKey, string errorViewName, IFlightRepository flightRepository)
{
_flightIdRouteKey = flightIdRouteKey;
_errorViewName = errorViewName;
_flightRepo = flightRepository;
}
public override async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
{
int flightId = (int)context.RouteData.Values[_flightIdRouteKey];
var result = await _flightRepo.GetFlightById(flightId);
if (!result.Valid)
{
context.Result = new ViewResult
{
ViewName = _errorViewName,
ViewData = new ViewDataDictionary(result.ViewData)
{
Model = model
}
};
return;
}
await next();
}
}
Now you can use the filter like this:
[TypeFilter(typeof(FlightValidator), Arguments = new object[] { "id", "ErrorPage"})]
public async Task<IActionResult> method(string id)
{
var viewModel = new FlightViewModel
{
Flight = result.Result
};
return View(viewModel);
}
I suggest you to refer Filters docs for more information about filters.

If you use a static method like this:
static async Task<IActionResult> ProcessAsync<T>(
Func<Task<RepositoryResult<T>>> process,
Func<T, IActionResult> ifValid
)
{
var result = await process();
if (!result.Valid)
{
return View("ErrorPage", result.Error.Message);
}
return ifValid(result.Result);
}
Then you can use it like this:
public Task<IActionResult> method(string id)
{
return ProcessAsync(
() => _flightRepository.GetLightById(id),
flight =>
{
var viewModel = new FlightViewModel
{
Flight = flight
};
return View(viewModel);
}
);
}
The static method can be defined anywhere you wish - in a base Controller class, or in a different namespace entirely (in which case you would import it with using static Some.Namespace.With.Class;.
Additionally, I suggest you use the convention of an Async suffix for asynchronous methods - so because GetLightById returns Task<T> I suggest renaming it GetLightByIdAsync.

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

Rendering ActionResult to string - comes out in incorrect order

I have an attempted solution at rendering an ActionResult to a string. I do this by passing in my own HttpContext which substitutes the Output text writer with my own TextWriter.
Here's the problem - the elements are rendering out of order. If I render the partial view by querying it directly through the browser, it works fine. If I render it through my substituted text writer, any #Html.Action elements within the razor view are rendered first, regardless of their position within the view.
So, here's my Razor view:
#inherits System.Web.Mvc.WebViewPage<WebsitePresentationLayer.MgrScreenLayoutViewer>
#using System.Web.Mvc.Html;
<div>
#Model.DebugText
</div>
#foreach (var item in #Model.Items)
{
<div>#item.Title</div>
#Html.Action(
"LayoutItem",
new
{
id = item.Id,
uniqueName = item.UniqueName
}
);
}
If I query the view directly via the browser, it renders in the correct order:
#Model.DebugText
Item1.Title
Item1 Action Rendering
Item2.Title
Item2 Action Rendering
If I render this to my TextWriter, it renders in the following order:
Item1 Action Rendering
Item2 Action Rendering
#Model.DebugText
Item1.Title
Item2.Title
Why?
Here's how I'm subsituting the Text writer. (I'm calling this from an ASP.NET WebForms page, so there is already an existing HttpContext)
public static class ActionResultExtensions
{
internal class MyResponseWrapper : HttpResponseWrapper
{
private System.IO.TextWriter _textWriter;
public MyResponseWrapper(HttpResponse wrappedResponse, System.IO.TextWriter textWriter)
: base(wrappedResponse)
{
_textWriter = textWriter;
}
public override System.IO.TextWriter Output
{
get { return this._textWriter; }
set { this._textWriter = value; }
}
}
internal class MyHttpContextWrapper : HttpContextWrapper
{
private readonly System.IO.TextWriter _textWriter;
public MyHttpContextWrapper(System.IO.TextWriter textWriter)
: base(HttpContext.Current)
{
this._textWriter = textWriter;
}
public override HttpResponseBase Response
{
get
{
var httpResponse = HttpContext.Current.Response;
return new MyResponseWrapper(httpResponse, this._textWriter);
}
}
}
public static void Render(this System.Web.Mvc.ActionResult result, System.IO.TextWriter textWriter, System.Web.Routing.RouteData routeData, System.Web.Mvc.ControllerBase controllerBase)
{
var httpContextWrapper = new MyHttpContextWrapper(textWriter);
result.ExecuteResult(new System.Web.Mvc.ControllerContext(httpContextWrapper, routeData, controllerBase));
}
}
public static class MvcUtils
{
public static void RenderControllerAction<T>(Func<T, System.Web.Mvc.ActionResult> f, System.IO.TextWriter writer) where T : System.Web.Mvc.ControllerBase, new()
{
var controller = new T();
// We have to initialise the RouteData so that it knows the name of the controller
// This is used to locate the view
var typeName = controller.GetType().Name;
System.Text.RegularExpressions.Regex regex = new System.Text.RegularExpressions.Regex("(.*)Controller$");
var match = regex.Match(typeName);
if (match.Success)
{
typeName = match.Groups[1].Value;
}
var routeData = new System.Web.Routing.RouteData();
routeData.Values.Add("controller", typeName);
var actionResult = f(controller);
actionResult.Render(writer, routeData, controller);
}
}
And then I finally output it to string using the following code:
StringBuilder sb = new StringBuilder();
StringWriter stringWriter = new StringWriter(sb);
CMS.Website.MvcUtils.RenderControllerAction<PlayerGroupController>
(
c => c.ScreenLayout(this.MgrPlayerGroupViewer.ScreenLayoutId),
stringWriter
);
stringWriter.Flush();
var generatedString = sb.ToString();
I've written an interceptor for the TextWriter, and sure enough, it's receiving three calls to Write(string)
Write(LayoutItem 1 action contents)
Write(LayoutItem 2 action contents)
Write(Model.DebugText and the two item titles)

I went through this about 6 months ago. Goal was to use a partial to populate a jquery popup dialog.
The problem is the View Engine wants to Render them in it's own awkward order...
Try this. LMK if it needs clarification.
public static string RenderPartialViewToString(Controller thisController, string viewName, object model)
{
// assign the model of the controller from which this method was called to the instance of the passed controller (a new instance, by the way)
thisController.ViewData.Model = model;
// initialize a string builder
using (StringWriter sw = new StringWriter())
{
// find and load the view or partial view, pass it through the controller factory
ViewEngineResult viewResult = ViewEngines.Engines.FindPartialView(thisController.ControllerContext, viewName);
ViewContext viewContext = new ViewContext(thisController.ControllerContext, viewResult.View, thisController.ViewData, thisController.TempData, sw);
// render it
viewResult.View.Render(viewContext, sw);
//return the razorized view/partial-view as a string
return sw.ToString();
}
}

Posting data when my view model has a constructor does not work

I have the following code:
[HttpGet]
public ActionResult Edit(int req)
{
var viewModel = new EditViewModel();
viewModel.RequestId = int;
return View(viewModel);
}
[HttpPost]
Public ActionResult Edit(EditViewModel viewModel)
{
// some code here...
}
It works fine: when the edit form is posted, I have the action controller who is called.
Now I modify some little bit my code like this:
[HttpGet]
public ActionResult Edit(int req)
{
var viewModel = new EditViewModel(req);
return View(viewModel);
}
[HttpPost]
Public ActionResult Edit(EditViewModel viewModel)
{
// some code here...
}
public class EditViewModel()
{
public EditViewModel(int req)
{
requestId = req;
}
...
}
In this new version, I have a view model with a contructor.
This time, when my form is posted back, the action controller is never triggered.
Any idea?
Thanks.

That's normal. The default model binder can no longer instantiate your view model as it doesn't have a parameterless constructor. You will have to write a custom model binder if you want to use view models that don't have a default constructor.
Normally you don't need such custom constructor. You could simply have your view model like that:
public class EditViewModel()
{
public int RequestId { get; set; }
}
and the POST action like that:
[HttpPost]
public ActionResult Edit(EditViewModel viewModel)
{
// some code here...
}
and now all you have to do is POST the requestId parameter instead of req and the default model binder will do the job.
And if for some reason you wanted to use a view model with custom constructor, here's an example of how the custom model binder might look like:
public class EditViewModelBinder : DefaultModelBinder
{
protected override object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType)
{
var req = bindingContext.ValueProvider.GetValue("req");
if (req == null)
{
throw new Exception("missing req parameter");
}
int reqValue;
if (!int.TryParse(req.AttemptedValue, out reqValue))
{
throw new Exception(string.Format("The req parameter contains an invalid value: {0}", req.AttemptedValue));
}
return new EditViewModel(reqValue);
}
}
which will be registered in your Application_Start:
ModelBinders.Binders.Add(typeof(EditViewModel), new EditViewModelBinder());

Asp.Net Core version
public class EditViewModelBinder : IModelBinder
{
public Task BindModelAsync(ModelBindingContext bindingContext)
{
if (bindingContext == null)
{
throw new ArgumentNullException(nameof(bindingContext));
}
var req = bindingContext.ValueProvider.GetValue("req");
if (req == ValueProviderResult.None || string.IsNullOrEmpty(req.FirstValue))
{
bindingContext.ModelState.TryAddModelError("req", "Missing req parameter");
}
int reqValue;
if (!int.TryParse(req.AttemptedValue, out reqValue))
{
bindingContext.ModelState.TryAddModelError($"The req parameter contains an invalid value: {req.AttemptedValue}");
}
var model = new EditViewModel(req.FirstValue);
bindingContext.Result = ModelBindingResult.Success(model);
return Task.CompletedTask;
}
}
You don't need to register anything with startup.cs anymore. Just assign the binder to your ViewModel and you're away.
[ModelBinder(BinderType = typeof(EditViewModelBinder))]
public class EditViewModel

t4mvc actionresult Converted to string

I'm trying to get from a T4MVC ActionResult to execute the call and get the entire string from inside a static function in my EmailService class. Any help would be much appreciated
Something like this
static string ExecuteAction(ActionResult result)
{
/* Code goes here */
}
So that I can call the function like this
public static class EmailService
{
public static bool SendWelcomeEmail(string name, string email)
{
var message = ExecuteAction(MVC.Emails.WelcomeEmail(name, email));
/* Other code */
}
}

I have done this very thing
protected virtual string RenderPartialViewToString(string viewName, object model)
{
if (string.IsNullOrEmpty(viewName))
viewName = ControllerContext.RouteData.GetRequiredString("action");
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();
}
}
you would implement it like this
string body = RenderPartialViewToString("PasswordChangedEmail");
the partial is just a partial view, however, there isnt any reason a full view couldnt be used. Hope it helps.

You won't be able to use the T4MVC ActionResults to do this as they have an empty ExecuteResult() implementation.
I can see two obvious ways that you may approach this:
1.create an instance of the controller on which the action method lies that you wish to call and then call it. You may decide to get an instance from the ControllerFactory instead of instantiating the class directly, although if you know what type it is, I'd go with instantiating an instance from the type directly.
to get a controller from the default controller factory, you can use
ControllerBuilder.Current.GetControllerFactory().CreateController(RequestContext requestContext, string controllerName);
This returns an IController so you'll need to cast it to the right controller type in order to call an action method. It's easier to just instantiate one directly :)
2.Use an email templating solution such as Postal, ActionMailer, MvcMailer or Kazi's Email Template Engine. All take advantage of Razor so you can have nicely templated email messages.

In case anyone is interested in the answer:
private static RequestContext RequestContext(this HttpContext context)
{
var httpContextBase = new HttpContextWrapper(context);
var routeData = new RouteData();
return new RequestContext(httpContextBase, routeData);
}
private static RouteData GetRoute(this ActionResult url)
{
var data = url.GetRouteValueDictionary();
var route = new RouteData();
foreach (var item in data)
route.Values[item.Key] = item.Value;
return route;
}
public static string ExecuteAsString(this T4MVC_ActionResult result)
{
var controllerName = result.Controller;
var context = HttpContext.Current.RequestContext();
context.RouteData = result.GetRoute();
var controller = (ControllerBase)ControllerBuilder.Current.GetControllerFactory().CreateController(context, controllerName);
controller.ControllerContext = new ControllerContext(context, controller);
var htmlHelper = new HtmlHelper(new ViewContext(
controller.ControllerContext,
new WebFormView(controller.ControllerContext, "HACK"),
new ViewDataDictionary(),
new TempDataDictionary(),
new StringWriter()),
new ViewPage());
return htmlHelper.Action(result).ToString();
}

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