Generating HTML email body in C

Question

Is there a better way to generate HTML email in C   for sending via System Net Mail   than using a Stringbuilder to do the following   string userName    John Doe   StringBuilder mailBody   new StringBuilder    mailBody AppendFormat   lt h1 gt Heading Here lt  h1 gt     mailBody AppendFormat  Dear  0    userName   mailBody AppendFormat   lt br   gt     mailBody AppendFormat   lt p gt First part of the email body goes here lt  p gt       and so on  and so forth

User · Answer

Use the System Web UI HtmlTextWriter class   StringWriter writer   new StringWriter    HtmlTextWriter html   new HtmlTextWriter writer    html RenderBeginTag HtmlTextWriterTag H1   html WriteEncodedText  Heading Here    html RenderEndTag    html WriteEncodedText String Format  Dear  0    userName    html WriteBreak    html RenderBeginTag HtmlTextWriterTag P   html WriteEncodedText  First part of the email body goes here    html RenderEndTag    html Flush     string htmlString   writer ToString      For extensive HTML that includes the creation of style attributes HtmlTextWriter is probably the best way to go   However it can be a bit clunky to use and some developers like the markup itself to be easily read but perversly HtmlTextWriter s choices with regard indentation is a bit wierd   In this example you can also use XmlTextWriter quite effectively -  writer   new StringWriter    XmlTextWriter xml   new XmlTextWriter writer   xml Formatting   Formatting Indented  xml WriteElementString  h1    Heading Here    xml WriteString String Format  Dear  0    userName    xml WriteStartElement  br    xml WriteEndElement    xml WriteElementString  p    First part of the email body goes here    xml Flush

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Updated Answer    The documentation for SmtpClient  the class used in this answer  now reads   Obsolete  SmtpClient and its network of types are poorly designed  we strongly recommend you use https   github com jstedfast MailKit and https   github com jstedfast MimeKit instead       Source  https   www infoq com news 2017 04 MailKit-MimeKit-Official  Original Answer   Using the MailDefinition class is the wrong approach  Yes  it s handy  but it s also primitive and depends on web UI controls--that doesn t make sense for something that is typically a server-side task   The approach presented below is based on MSDN documentation and Qureshi s post on CodeProject com   NOTE  This example extracts the HTML file  images  and attachments from embedded resources  but using other alternatives to get streams for these elements are fine  e g  hard-coded strings  local files  and so on   Stream htmlStream   null  Stream imageStream   null  Stream fileStream   null  try              Create the message          var from   new MailAddress FROM EMAIL  FROM NAME           var to   new MailAddress TO EMAIL  TO NAME           var msg   new MailMessage from  to           msg Subject   SUBJECT          msg SubjectEncoding   Encoding UTF8                Get the HTML from an embedded resource          var assembly   Assembly GetExecutingAssembly            htmlStream   assembly GetManifestResourceStream HTML RESOURCE PATH                 Perform replacements on the HTML file  if you re using it as a template           var reader   new StreamReader htmlStream           var body   reader                  ReadToEnd                    Replace   TEMPLATE TOKEN1    TOKEN1 VALUE                   Replace   TEMPLATE TOKEN2    TOKEN2 VALUE      and so on                  Create an alternate view and add it to the email          var altView   AlternateView CreateAlternateViewFromString body  null  MediaTypeNames Text Html           msg AlternateViews Add altView                 Get the image from an embedded resource  The  lt img gt  tag in the HTML is                      lt img src  pid IMAGE PNG  gt          imageStream   assembly GetManifestResourceStream IMAGE RESOURCE PATH           var linkedImage   new LinkedResource imageStream   image png            linkedImage ContentId    IMAGE PNG           altView LinkedResources Add linkedImage                 Get the attachment from an embedded resource          fileStream   assembly GetManifestResourceStream FILE RESOURCE PATH           var file   new Attachment fileStream  MediaTypeNames Application Pdf           file Name    FILE PDF           msg Attachments Add file                 Send the email         var client   new SmtpClient               client Credentials   new NetworkCredential               client Send msg     finally           if  fileStream    null  fileStream Dispose            if  imageStream    null  imageStream Dispose            if  htmlStream    null  htmlStream Dispose

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I use dotLiquid for exactly this task   It takes a template  and fills special identifiers with the content of an anonymous object     define template String templateSource     lt h1 gt   Heading   lt  h1 gt Dear   UserName    lt br  gt  lt p gt First part of the email body goes here    Template bodyTemplate   Template Parse templateSource      Parses and compiles the template source    Create DTO for the renderer var bodyDto   new       Heading    Heading Here       UserName   userName    String bodyText   bodyTemplate Render Hash FromAnonymousObject bodyDto      It also works with collections  see some online examples

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A commercial version which I use in production and allows for easy maintenance is LimiLabs Template Engine  been using it for 3  years and allows me to make changes to the text template without having to update code  disclaimers  links etc    - it could be as simple as Contact templateData         string html   Template       FromFile  quot template txt quot         DataFrom templateData         Render     Worth taking a look at  like I did  after attempting various answers mentioned here

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You can use the MailDefinition class   This is how you use it   MailDefinition md   new MailDefinition    md From    test domain com   md IsBodyHtml   true  md Subject    Test of MailDefinition    ListDictionary replacements   new ListDictionary    replacements Add   name     Martin    replacements Add   country     Denmark     string body     lt div gt Hello  name  You re from  country   lt  div gt     MailMessage msg   md CreateMailMessage  you anywhere com   replacements  body  new System Web UI Control       Also  I ve written a blog post on how to generate HTML e-mail body in C  using templates using the MailDefinition class

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If you don t want a dependency on the full  NET Framework  there s also a library that makes your code look like   string userName    John Doe    var mailBody   new HTML       new H 1             Heading Here             new P           string Format  Dear  0     userName           new Br              new P            First part of the email body goes here            string htmlString   mailBody Render      It s open source  you can download it from http   sourceforge net projects htmlplusplus   Disclaimer  I m the author of this library  it was written to solve the same issue exactly - send an HTML email from an application

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As an alternative to MailDefinition  have a look at RazorEngine https   github com Antaris RazorEngine   This looks like a better solution   Attributted to     how to send email wth email template c   E g  using RazorEngine  using RazorEngine Templating  using System   namespace RazorEngineTest       class Program               static void Main string   args                string template          lt h1 gt Heading Here lt  h1 gt  Dear  Model UserName   lt br   gt   lt p gt First part of the email body goes here lt  p gt         const string templateKey    tpl           Better to compile once     Engine Razor AddTemplate templateKey  template       Engine Razor Compile templateKey           Run is quicker than compile and run     string output   Engine Razor Run          templateKey           model  new                       UserName    Fred                   Console WriteLine output                       Which outputs      lt h1 gt Heading Here lt  h1 gt  Dear Fred   lt br   gt   lt p gt First part of the email body goes here lt  p gt       Heading Here Dear Fred   First part of the email   body goes here

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I would recomend using templates of some sort  There are various different ways to approach this but essentially hold a template of the Email some where  on disk  in a database etc  and simply insert the key data  IE  Recipients name etc  into the template   This is far more flexible because it means you can alter the template as required without having to alter your code  In my experience your likely to get requests for changes to the templates from end users  If you want to go the whole hog you could include a template editor

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You might want to have a look at some of the template frameworks that are available at the moment  Some of them are spin offs as a result of MVC but that isn t required  Spark is a good one

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Emitting handbuilt html like this is probably the best way so long as the markup isn t too complicated  The stringbuilder only starts to pay you back in terms of efficiency after about three concatenations  so for really simple stuff string   string will do   Other than that you can start to use the html controls  System Web UI HtmlControls  and render them  that way you can sometimes inherit them and make your own clasess for complex conditional layout

[c#] Generating HTML email body in C#

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