How to include HTML document in .NET application with variable fields?

Question

I have a C#/.NET app which currently uses StringBuilder to generate an HTML email message.

A new message format has been developed and now includes more formatting and CSS. I'd like to avoid appending each line of the file using StringBuilder, so I thought it best to include the HTML file as a resource.

However, there are about 21 variables within the CSS and HTML which I need to change on the fly. My first thought was to replace them with the standard String.Format placeholders ({0}, {1} etc) but when viewing the HTML, validation complains about these.

I'm rather stumped as to what the best practice is for storing a 200-line HTML file and changing parts of it before inclusion in an email.

Example:

Within the CSS, I need to change the color of certain elements, like this:

#header
{
    background-color: {0};
}

And within the HTML, I need to change strings and URLs, like this:

<img src="{1}" />
<span>{2}</span>

It seems including the HTML as a resource in the project would be best, but trying to use String.Format with that resource, regardless if it would work, is a poor method because of the aforementioned validation errors.

Any suggestions?

why is it a problem that validation fails on the "template HTML" before the placeholders are replaced ? IMHO the only important point is the it validates correctly AFTER replacing the placeholders with some content! — Yahia, May 18 '12 at 17:13
Then you'd have to remember which means what. And you need maintain argument count consistent. Use replaceable tokens like <%token_name%> and create simple find-replace method to replace tokens from some dictionary. — Val Bakhtin, May 18 '12 at 17:13
This question is like a rose in a Stack Overflow full of weeds. I hope it gets an answer. — Kendall Frey, May 18 '12 at 17:20

Asif Mushtaq · Answer 1 · 2012-05-18T17:28:29.000

5

I think you can try t4 tamplate

With t4 template you can even do more complex things like

<table>
<# for (int i = 1; i <= 10; i++)
   { #>
     <tr><td>Test name <#= i #> </td>
         <td>Test value <#= i * i #> </td> </tr>
 <# } #>
</table>

edited May 18 '12 at 17:28

answered May 18 '12 at 17:13

Asif Mushtaq

13,010
3
33
42

score 3 · Answer 2 · edited May 23 '17 at 12:29

3

You can use the Razor engine to render a HTML string:

<h2>Items:</h2>
@foreach(var item in list)
{
    <p>Item: @item.Description</p>
}

These answers Is it possible to use Razor View Engine outside asp.net give some nice links to do so.

edited May 23 '17 at 12:29

Community

1
1

answered May 18 '12 at 17:39

Lucas Reis

743
11
21

score 2 · Accepted Answer · answered May 18 '12 at 17:14

2

Instead of using {1} use a name e.g. Table1HeaderImage, then instead of using String.Format use String.Replace. You could have a collection of thingies to put in thehtml then, a quick loop, even extra attributes for customisation from users version, etc.

answered May 18 '12 at 17:14

Tony Hopkinson

20,172
3
31
39

My middle name, well part of it. :) – Tony Hopkinson May 19 '12 at 13:00

score 2 · Answer 4 · answered May 19 '12 at 08:37

2

You could create a preprocessed T4 text template file. http://msdn.microsoft.com/en-us/library/ee844259 One of the nice features T4 text templates is that they can be used to auto generate any kind of text file.

answered May 19 '12 at 08:37

BenCamps

1,694
15
25

score 0 · Answer 5 · answered May 18 '12 at 17:16

0

What I do is something like this:

StreamReader reader = new StreamReader(Server.MapPath("Email/email.html"));
string email_html = reader.ReadToEnd();
reader.Close();

email_html = email_html.Replace("[link]", activation_link);

answered May 18 '12 at 17:16

vpascoal

278
2
4
15

This is essentially what I went with; thanks for the suggestion. – JYelton May 18 '12 at 20:31

score 0 · Answer 6 · answered May 18 '12 at 17:54

I would use <%0%>, <%1%>, etc. instead of {0}, {1}, etc.

At runtime, you would:

Replace all { with {{ and } with }}
Replace all <% with { and %> with }
String.Format()

You could also do as Val Bakhtin suggested, and use names instead of numbers. Then the process would be simply:

Replace all <%name%> with dictionary["name"]

How to include HTML document in .NET application with variable fields?

6 Answers6