RazorEngine string layouts and sections?

Question

I use razor engine like this:

public class EmailService : IService
{
    private readonly ITemplateService templateService;

    public EmailService(ITemplateService templateService)
    {
        if (templateService == null)
        {
            throw new ArgumentNullException("templateService");
        }
        this.templateService = templateService;
    }

    public string GetEmailTemplate(string templateName)
    {
        if (templateName == null)
        {
            throw new ArgumentNullException("templateName");
        }
        Assembly assembly = Assembly.GetAssembly(typeof(EmailTemplate));
        Stream stream = assembly.GetManifestResourceStream(typeof(EmailTemplate), "{0}.cshtml".FormatWith(templateName));
        string template = stream.ReadFully();
        return template;
    }

    public string GetEmailBody(string templateName, object model = null)
    {
        if (templateName == null)
        {
            throw new ArgumentNullException("templateName");
        }
        string template = GetEmailTemplate(templateName);
        string emailBody = templateService.Parse(template, model, null, null);
        return emailBody;
    }
}

The templating service I use is injected although it's just a default implementation:

    internal ITemplateService InstanceDefaultTemplateService()
    {
        ITemplateServiceConfiguration configuration = new TemplateServiceConfiguration();
        ITemplateService service = new TemplateService(configuration);
        return service;
    }

Since in this case in particular I will be building emails from these templates. I want to be able to use @sections for the email'a subject, and different sections of the email body, while using a layout where I specify the styles that are common to the whole email structure (which will look like one of MailChimp's probably).

The question is then twofold:

• How can I specify layouts in RazorEngine?
• How can I specify these layouts from strings (or a stream)? since as you can see, I use embedded resources to store the razor email templates.

Update

Maybe I wasn't clear, but I'm referring to the RazorEngine library.

Answer 1

Turns out after some digging that layouts are supported, we just have to declare them with _Layout instead of Layout

As for the embedded resource issue, I implemented the following ITemplateResolver

using System;
using System.IO;
using System.Reflection;
using Bruttissimo.Common;
using RazorEngine.Templating;

namespace Website.Extensions.RazorEngine
{
    /// <summary>
    /// Resolves templates embedded as resources in a target assembly.
    /// </summary>
    public class EmbeddedTemplateResolver : ITemplateResolver
    {
        private readonly Assembly assembly;
        private readonly Type type;
        private readonly string templateNamespace;

        /// <summary>
        /// Specify an assembly and the template namespace manually.
        /// </summary>
        /// <param name="assembly">The assembly where the templates are embedded.</param>
        /// <param name="templateNamespace"></param>
        public EmbeddedTemplateResolver(Assembly assembly, string templateNamespace)
        {
            if (assembly == null)
            {
                throw new ArgumentNullException("assembly");
            }
            if (templateNamespace == null)
            {
                throw new ArgumentNullException("templateNamespace");
            }
            this.assembly = assembly;
            this.templateNamespace = templateNamespace;
        }

        /// <summary>
        /// Uses a type reference to resolve the assembly and namespace where the template resources are embedded.
        /// </summary>
        /// <param name="type">The type whose namespace is used to scope the manifest resource name.</param>
        public EmbeddedTemplateResolver(Type type)
        {
            if (type == null)
            {
                throw new ArgumentNullException("type");
            }
            this.assembly = Assembly.GetAssembly(type);
            this.type = type;
        }

        public string Resolve(string name)
        {
            if (name == null)
            {
                throw new ArgumentNullException("name");
            }
            Stream stream;
            if (templateNamespace == null)
            {
                stream = assembly.GetManifestResourceStream(type, "{0}.cshtml".FormatWith(name));
            }
            else
            {
                stream = assembly.GetManifestResourceStream("{0}.{1}.cshtml".FormatWith(templateNamespace, name));
            }
            if (stream == null)
            {
                throw new ArgumentException("EmbeddedResourceNotFound");
            }
            string template = stream.ReadFully();
            return template;
        }
    }
}

Then you just wire it like this:

    internal static ITemplateService InstanceTemplateService()
    {
        TemplateServiceConfiguration configuration = new TemplateServiceConfiguration
        {
            Resolver = new EmbeddedTemplateResolver(typeof(EmailTemplate))
        };
        ITemplateService service = new TemplateService(configuration);
        return service;
    }

The type you pass is just for referencing the assembly and namespace where the resources are embedded.

namespace Website.Domain.Logic.Email.Template
{
    /// <summary>
    /// The purpose of this class is to expose the namespace of razor engine templates in order to
    /// avoid having to hard-code it when retrieving the templates embedded as resources.
    /// </summary>
    public sealed class EmailTemplate
    {
    }
}

One last thing, in order to have the templates resolved with our resolver we have to resolve them like this:

ITemplate template = templateService.Resolve(templateName, model);
string body = template.Run();
return body;

.Run is just a simple extension method since I can't find any use for a ViewBag.

public static class ITemplateExtensions
{
    public static string Run(this ITemplate template)
    {
        ExecuteContext context = new ExecuteContext();
        string result = template.Run(context);
        return result;
    }
}

UPDATE

Here are the missing extensions

    public static string FormatWith(this string text, params object[] args)
    {
        return string.Format(text, args);
    }

    public static string ReadFully(this Stream stream)
    {
        using (StreamReader reader = new StreamReader(stream))
        {
            return reader.ReadToEnd();
        }
    }

Answer 2

I needed to supply my own layout as either a string or a file name. Here is how I solved this (based on this blog post)

public static class RazorEngineConfigurator
{
    public static void Configure()
    {
        var templateConfig = new TemplateServiceConfiguration
            {
                Resolver = new DelegateTemplateResolver(name =>
                    {
                        //no caching cause RazorEngine handles that itself
                        var emailsTemplatesFolder = HttpContext.Current.Server.MapPath(Properties.Settings.Default.EmailTemplatesLocation);
                        var templatePath = Path.Combine(emailsTemplatesFolder, name);
                        using (var reader = new StreamReader(templatePath)) // let it throw if doesn't exist
                        {
                            return reader.ReadToEnd();
                        }
                    })
            };
        RazorEngine.Razor.SetTemplateService(new TemplateService(templateConfig));
    }
}

Then I call RazorEngineConfigurator.Configure() in Global.asax.cs and it's ready.

The path to my templates is in Properties.Settings.Default.EmailTemplatesLocation

In my view I have this:

@{ Layout = "_layout.html";}

_layout.html is in emailsTemplatesFolder

It's a pretty standard HTML with a @RenderBody() call in the middle.

As far as I understand, RazorEngine uses the template name ("_layout.html" in this case) as a key to its cache so the delegate in my configurator is called only once per template.

I think it uses that resolver for every template name it doesn't know (yet).