Generate Email HTML using Razor in an ASP.NET MVC Project

Question

I have an ASP.NET MVC project that uses Razor for rendering HTML using the built-in engine.

I would like to create Email Templates using the same process. Usually, these templates are created as part of a Action Context (for instance, when a user has completed a purchase, a notification would be sent). However, there are some instances where there is no context available. For instance, sending a log when the application is restarting.

This is what I have come up with so far:

public static string RenderRazor(ViewTemplateType TemplateType, string ViewName, PageController Controller = null, object Model = null)
{
    try
    {
        ControllerContext Context;

        if (Controller != null)
        {
            Context = Controller.ControllerContext;
        }
        else
        {
            if (HttpContext.Current == null)
            {
                throw new InvalidOperationException("Cannot render a razor template if the current context is null (See DEV-1669).");
            }
            var RouteData = new RouteData();
            RouteData.Values.Add("controller", "Pseudo");
            Controller = new PseudoController(Model);
            Context = new ControllerContext(new HttpContextWrapper(HttpContext.Current), RouteData, Controller);
            // If this isn't set, an error occurs when calling FindView/FindViewPartial.
            Controller.ControllerContext = Context;
        }

        // I'm not really sure what the point of this is...
        // Further, it was actually causing an exception to occur since the Controller may not actually be populated?
        // Without this, the Notification Debug wasn't working - so apparently it is required in some circumstances for notifications.
        if (Controller != null && Controller.ViewData != null && Model != null) { Controller.ViewData.Model = Model; }

        var ViewResult = ViewName.StartsWith("_")
            ? ViewEngines.Engines.FindPartialView(Context, string.Format("~/Views/Template/{0}/{1}.cshtml", TemplateType, ViewName))
            : ViewEngines.Engines.FindView(Context, string.Format("~/Views/Template/{0}/{1}.cshtml", TemplateType, ViewName), string.Format("~/Views/Template/{0}/_Shared/{1}.cshtml", TemplateType, "_Layout"));

        if (ViewResult.View == null)
        {
            StringBuilder LocationBuilder = new StringBuilder();
            string[] SearchedLocations = ViewResult.SearchedLocations.ToArray();
            for (int i = 0; i < SearchedLocations.Length; i++)
            {
                LocationBuilder.Append(string.Format("({0}) {1} ", i, SearchedLocations[i]));
            }

            throw new InvalidOperationException(string.Format("Could not find the {0} Template named {1} using the {2} Master. Locations Searched: {3}", TemplateType, ViewName, "_Layout", LocationBuilder));//
        }
        using (var Writer = new StringWriter())
        {
            //ViewResult.View.Render(new ViewContext(
            //  Context,
            //  ViewResult.View,
            //  (Controller != null) ? Controller.ViewData : (Model != null) ? new ViewDataDictionary(Model) : new ViewDataDictionary(),
            //  (Controller != null) ? Controller.TempData : new TempDataDictionary(), Writer), Writer);

            ViewResult.View.Render(new ViewContext(
                Context,
                ViewResult.View,
                Controller.ViewData,
                Controller.TempData, Writer), Writer);

            ViewResult.ViewEngine.ReleaseView(Context, ViewResult.View);

            // This must remove Tabs (\t) Returns (\r) and Newlines (\n)
            // Always making the quotes single makes sense for statically generated stuff - the only time when it wouldn't make sense is for more complex stuff or if it includes JS which i don't think
            // a statically generated one should ever?

            string result = Regex.Replace(Writer.GetStringBuilder().ToString().Replace("\"", "\'"), "(\\t|\\r|\\n)", string.Empty);

            // Currently, this process does not work well when initiated outside of a request (e.g. in the startup method or purely within a
            // hangfire task). This serves as a warning if it ever is (since it will return an empty string).

            if (result.Blank()) { throw new InvalidOperationException("There was an error rendering the " + ViewName + " template. This can happen if the template was initialized outside of the context of an actual request."); }
            else
            {
                return result;
            }
        }
    }
    catch (Exception ex)
    {
        // This could indicate an error in the underlying template
        // If there is an error on any of the underlying templates in a given class,
        // this can be called.
        Logging.Error(ex);
        return string.Empty;
    }
}

This works pretty well except for when I am trying to generate a template when I don't have a reference to a Controller.

I have also started looking into applying the third-party RazorEngine (https://antaris.github.io/RazorEngine) - but is this overkill? Is it even feasible to implement this in a project that also utilizes the built-in razor engine?

Jasen · Accepted Answer · 2017-11-21 01:08:54Z

I've used ActionMailer in the past. It's no longer maintained but there's a fork https://github.com/crossvertise/ActionMailerNext.

You set up a controller to bind the templates but can call it like another service class.

public class EmailController : MailerBase, IEmailService
{
    public EmailResult PasswordRecovery(PasswordRecoveryModel model)
    {
        To.Add(model.Email);
        From = "[email protected]";
        Subject = "Password Recovery";
        return Email("PasswordRecovery", model);
    }
}

I set it up with my own interface so I can inject it wherever

public interface IEmailService
{
    EmailResult PasswordRecovery(PasswordRecoveryModel model);
}


public class Foo
{
    private readonly IEmailService emailService;

    public Foo(IEmailService emailService)
    {
        this.emailService = emailService;
    }

    public void DoSomething()
    {
        this.emailService.PasswordRecovery(new PasswordRecoveryModel { ... });
    }
}

The templates look just like regular views

PasswordRecovery.html.cshtml

@using ActionMailer.Net.Mvc
@model PasswordRecoveryModel

<p>@Model.UserName</p>
<div> ... </div>

I haven't tried the fork so I can only assume it's similar in usage.

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