Can I set up HTML/Email Templates with ASP.NET?

Question

I'm working on a site that will send out a significant number of emails. I want to set up both header and footer text, or maybe even templates to allow the users to easily edit these emails if they need to.

If I embed the HTML inside C# string literals, it's ugly and they would have to worry about escaping. Including flat files for the header and footer might work, but something about it just doesn't feel right.

What would be ideal what be to use a .ASPX page as a template somehow, then just tell my code to serve that page, and use the HTML returned for the email.

Is there a nice and easy way to do this? Is there a better way to go about solving this problem?

Updated:
I added an answer that enables you to use a standard .aspx page as the email template. Just replace all the variables like you normally would, use databinding, etc. Then just capture the output of the page, and voila! You have your HTML email!

UPDATED WITH CAVEAT!!!:
I was using the MailDefinition class on some aspx pages just fine, but when trying to use this class during a server process that was running, it failed. I believe it was because the MailDefinition.CreateMailMessage() method requires a valid control to reference, even though it doesn't always do something. Because of this, I would recommend my approach using an aspx page, or Mun's approach using an ascx page, which seems a little better.

Answer 1

I think the easy answer is MvcMailer. It s NuGet package that lets you use your favorite view engine to generate emails. See the NuGet package here and the project documentation

Hope it helps!

Answer 2

I think you could also do something like this:

Create and .aspx page, and put this at the end of the OnLoad method, or call it manually.

    StringBuilder sb = new StringBuilder();
    StringWriter sw = new StringWriter(sb);
    HtmlTextWriter htmlTW = new HtmlTextWriter(sw);
    this.Render(htmlTW);

I'm not sure if there are any potential issues with this, but it looks like it would work. This way, you could use a full featured .aspx page, instead of the MailDefinition class which only supports Text replacements.

Answer 3

@bardev provides a good solution, but unfortunately it's not ideal in all cases. Mine was one of them.

I'm using WebForms in a Website (I swear I'll never use a Website again--what a PITA) in VS 2013.

I tried the Razor suggestion, but mine being a Website I didn't get the all-important IntelliSense that the IDE delivers in an MVC project. I also like to use the designer for my templates--a perfect spot for a UserControl.

Nix on Razor again.

So I came up with this little framework instead (hat tips to @mun for UserControl and @imatoria for Strong Typing). Just about the only potential trouble spot I can see is that you have to be careful to keep your .ASCX filename in sync with its class name. If you stray, you'll get a runtime error.

FWIW: In my testing at least the RenderControl() call doesn't like a Page control, so I went with UserControl.

I'm pretty sure I've included everything here; let me know if I left something out.

HTH

Usage:

Partial Class Purchase
  Inherits UserControl

  Private Sub SendReceipt()
    Dim oTemplate As MailTemplates.PurchaseReceipt

    oTemplate = MailTemplates.Templates.PurchaseReceipt(Me)
    oTemplate.Name = "James Bond"
    oTemplate.OrderTotal = 3500000
    oTemplate.OrderDescription = "Q-Stuff"
    oTemplate.InjectCss("PurchaseReceipt")

    Utils.SendMail("{0} <[e-mail]>".ToFormat(oTemplate.Name), "Purchase Receipt", oTemplate.ToHtml)
  End Sub
End Class

Base Class:

Namespace MailTemplates
  Public MustInherit Class BaseTemplate
    Inherits UserControl

    Public Shared Function GetTemplate(Caller As TemplateControl, Template As Type) As BaseTemplate
      Return Caller.LoadControl("~/MailTemplates/{0}.ascx".ToFormat(Template.Name))
    End Function



    Public Sub InjectCss(FileName As String)
      If Me.Styler IsNot Nothing Then
        Me.Styler.Controls.Add(New Controls.Styler(FileName))
      End If
    End Sub



    Private ReadOnly Property Styler As PlaceHolder
      Get
        If _Styler Is Nothing Then
          _Styler = Me.FindNestedControl(GetType(PlaceHolder))
        End If

        Return _Styler
      End Get
    End Property
    Private _Styler As PlaceHolder
  End Class
End Namespace

"Factory" Class:

Namespace MailTemplates
  Public Class Templates
    Public Shared ReadOnly Property PurchaseReceipt(Caller As TemplateControl) As PurchaseReceipt
      Get
        Return BaseTemplate.GetTemplate(Caller, GetType(PurchaseReceipt))
      End Get
    End Property
  End Class
End Namespace

Template Class:

Namespace MailTemplates
  Public MustInherit Class PurchaseReceipt
    Inherits BaseTemplate

    Public MustOverride WriteOnly Property Name As String
    Public MustOverride WriteOnly Property OrderTotal As Decimal
    Public MustOverride WriteOnly Property OrderDescription As String
  End Class
End Namespace

ASCX Header:

<%@ Control Language="VB" ClassName="_Header" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional //EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<!--
  See https://www.campaignmonitor.com/blog/post/3317/ for discussion of DocType in HTML Email
-->

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <title></title>
  <asp:PlaceHolder ID="plcStyler" runat="server"></asp:PlaceHolder>
</head>
<body>

ASCX Footer:

<%@ Control Language="VB" ClassName="_Footer" %>

</body>
</html>

ASCX Template:

<%@ Control Language="VB" AutoEventWireup="false" CodeFile="PurchaseReceipt.ascx.vb" Inherits="PurchaseReceipt" %>

<%@ Register Src="_Header.ascx" TagName="Header" TagPrefix="uc" %>
<%@ Register Src="_Footer.ascx" TagName="Footer" TagPrefix="uc" %>

<uc:Header ID="ctlHeader" runat="server" />

  <p>Name: <asp:Label ID="lblName" runat="server"></asp:Label></p>
  <p>Order Total: <asp:Label ID="lblOrderTotal" runat="server"></asp:Label></p>
  <p>Order Description: <asp:Label ID="lblOrderDescription" runat="server"></asp:Label></p>

<uc:Footer ID="ctlFooter" runat="server" />

ASCX Template CodeFile:

Partial Class PurchaseReceipt
  Inherits MailTemplates.PurchaseReceipt

  Public Overrides WriteOnly Property Name As String
    Set(Value As String)
      lblName.Text = Value
    End Set
  End Property



  Public Overrides WriteOnly Property OrderTotal As Decimal
    Set(Value As Boolean)
      lblOrderTotal.Text = Value
    End Set
  End Property



  Public Overrides WriteOnly Property OrderDescription As Decimal
    Set(Value As Boolean)
      lblOrderDescription.Text = Value
    End Set
  End Property
End Class

Helpers:

'
' FindNestedControl helpers based on tip by @andleer
' at http://stackoverflow.com/questions/619449/
'

Public Module Helpers
  <Extension>
  Public Function AllControls(Control As Control) As List(Of Control)
    Return Control.Controls.Flatten
  End Function



  <Extension>
  Public Function FindNestedControl(Control As Control, Id As String) As Control
    Return Control.Controls.Flatten(Function(C) C.ID = Id).SingleOrDefault
  End Function



  <Extension>
  Public Function FindNestedControl(Control As Control, Type As Type) As Control
    Return Control.Controls.Flatten(Function(C) C.GetType = Type).SingleOrDefault
  End Function



  <Extension>
  Public Function Flatten(Controls As ControlCollection) As List(Of Control)
    Flatten = New List(Of Control)

    Controls.Traverse(Sub(Control) Flatten.Add(Control))
  End Function


  <Extension>
  Public Function Flatten(Controls As ControlCollection, Predicate As Func(Of Control, Boolean)) As List(Of Control)
    Flatten = New List(Of Control)

    Controls.Traverse(Sub(Control)
                        If Predicate(Control) Then
                          Flatten.Add(Control)
                        End If
                      End Sub)
  End Function



  <Extension>
  Public Sub Traverse(Controls As ControlCollection, Action As Action(Of Control))
    Controls.Cast(Of Control).ToList.ForEach(Sub(Control As Control)
                                               Action(Control)

                                               If Control.HasControls Then
                                                 Control.Controls.Traverse(Action)
                                               End If
                                             End Sub)
  End Sub



  <Extension()>
  Public Function ToFormat(Template As String, ParamArray Values As Object()) As String
    Return String.Format(Template, Values)
  End Function



  <Extension()>
  Public Function ToHtml(Control As Control) As String
    Dim oSb As StringBuilder

    oSb = New StringBuilder

    Using oSw As New StringWriter(oSb)
      Using oTw As New HtmlTextWriter(oSw)
        Control.RenderControl(oTw)
        Return oSb.ToString
      End Using
    End Using
  End Function
End Module



Namespace Controls
  Public Class Styler
    Inherits LiteralControl

    Public Sub New(FileName As String)
      Dim _
        sFileName,
        sFilePath As String

      sFileName = Path.GetFileNameWithoutExtension(FileName)
      sFilePath = HttpContext.Current.Server.MapPath("~/Styles/{0}.css".ToFormat(sFileName))

      If File.Exists(sFilePath) Then
        Me.Text = "{0}<style type=""text/css"">{0}{1}</style>{0}".ToFormat(vbCrLf, File.ReadAllText(sFilePath))
      Else
        Me.Text = String.Empty
      End If
    End Sub
  End Class
End Namespace



Public Class Utils
  Public Shared Sub SendMail(Recipient As MailAddress, Subject As String, HtmlBody As String)
    Using oMessage As New MailMessage
      oMessage.To.Add(Recipient)
      oMessage.IsBodyHtml = True
      oMessage.Subject = Subject.Trim
      oMessage.Body = HtmlBody.Trim

      Using oClient As New SmtpClient
        oClient.Send(oMessage)
      End Using
    End Using
  End Sub
End Class

Answer 4

Here is one more alternative that uses XSL transformations for more complex email templates: Sending HTML-based email from .NET applications.

Answer 5

i had a similar requirement on 1 of the projects where you had to send huge number of emails each day, and the client wanted complete control over html templates for different types of emails.

due to the large number of emails to be sent, performance was a primary concern.

what we came up with was static content in sql server where you save entire html template mark up (along with place holders, like [UserFirstName], [UserLastName] which are replaced with real data at run time) for different types of emails

then we loaded this data in asp.net cache - so we dont read the html templates over and over again - but only when they are actually changed

we gave the client a WYSIWYG editor to modify these templates via a admin web form. whenever updates were made, we reset asp.net cache.

and then we had a seperate table for email logs - where every email to be sent was logged. this table had fields called emailType, emailSent and numberOfTries.

we simply ran a job every 5 minutes for important email types (like new member sign up, forgot password) which need to be sent asap

we ran another job every 15 minutes for less important email types (like promotion email, news email, etc)

this way you dont block your server sending non stop emails and you process mails in batch. once an email is sent you set the emailSent field to 1.

Answer 6

Set the set the Email Message IsBodyHtml = true

Take your object that contains your email contents Serialize the object and use xml/xslt to generate the html content.

If you want to do AlternateViews do the same thing that jmein only use a different xslt template to create the plain text content.

one of the major advantages to this is if you want to change your layout all you have to do update the xslt template.