What would be considered the best way to architect sending email from a C# web application?

Question

I am working on a web application that will be going live soon, and I am now trying to figure out the best way for handling sending email from the application. I understand completely HOW to send email from the application using the MailMessage and SmtpClient classes, however my question is from a different angle. My main purpose at my job before this project was support of old applications that had been developed before my time. In these applications, when they needed to send email, they hard coded any of the messages into the actual message with all of the HTML tags embeded directly into the C# code.

The application that I am working on will have a template for the emails to be sent in, as a sort of styling container, and the different messages will be embeded into the main content div's of the template. I would like to avoid hardcoding these templates in this application, so I have been trying to figure out the best way to layout my project. I have thought of using a t4 template, and reading the different t4's into the application and applying a String.Format with the specified parameters to add names/emails to the messages to be sent. However, I am not sure this is the best way to do it.

My other idea was to define a class for each type of message, however this would end up hardcoding messages again, which as I said I don't want to do.

My question is, how have you approached this in the past? What worked, and what didn't and for what reasons? I have looked all over online, but either the only content out there is on HOW to send the message, or I have not used the right Google power words.

Answer 1

I do it this way:

• Code it the usual way with ViewModel and Razor Template
• By creating the e-mail, use http://razorengine.codeplex.com/ to load and parse the template
• Be aware to not use Html and Url helper if you want to send e-mails in a thread, because they rely on HttpContext which you don't have in that case. Build your own helpers if needed.

For example, if you have a ViewModel Car in your application which is displayed somewhere, you could also use this ViewModel as @model in a Razor Template for e-mail.

Answer 2

I've had to do this on a couple of occasions. I originally used the ASP.Net template engine based on I think a Rick Strahl blog post. It worked but there was always some issue I was banging my head against.

I switched to using the NVelocity template engine and found it a really simple way to create and maintain email templates. There are a number of other template engines and I suspect next time I might have a serious look at the Razor engine.

The code for merging values into the template:

private string Merge(ManualTypeEnum manualType, Object mergeValues)
{
    var body = "";
    var templateFile = string.Format("{0}MailTemplate.vm", manualType);
    var velocity = new VelocityEngine();
    var props = new ExtendedProperties();
    props.AddProperty("file.resource.loader.path", Config.EmailTemplatePath);
    velocity.Init(props);
    var template = velocity.GetTemplate(templateFile);
    var context = new VelocityContext();
    context.Put("Change", mergeValues);
    using (var writer = new StringWriter())
    {
        template.Merge(context, writer);
        body = writer.ToString();
    }
    return body;
}

The values to merge are passed as an anonymous object, and can include various types including lists etc e.g.

var emailBody = Merge(newDocument.ManualType, new
{
    ManualType = newDocument.ManualType.ToString(),
    Message = change.Message,
    NewTitle = newDocument.Title ?? "",
    NewVersion = newDocument.Version ?? "",
    Contact = From,
    Changes = change.ToList(),
});