ASP.NET SSI Server-Side Includes

SSI directives can be used on IIS.

They can include static resources in your ASP.NET website project. We explore details of server-side-include use and processing in ASP.NET pages.

Intro. First, SSI is not an ASP.NET technology, but server-side includes are supported on IIS. The following comment, in an ASP.NET aspx file, will tell the server (IIS) to insert the text of the file Style1-min.css where the HTML comment is.

The example snippet shows the "file" attribute. It points directly to the file "Style1-min.css" that is located in the Style folder at the root of the web project, relative to the page.

Also: The other option you can add to the #include is virtual, which uses virtual paths.

Include example

<!-- #include file="Style/Style1-min.css" -->

Uses. SSI directives are not great for many situations. Use them only for including static resources into .aspx pages. I decided on SSI as a good solution. I used it for including CSS markup into HTML headers.

Note: These CSS files needed to be minified, and the #include can include the minified files.

And: In the resulting HTML, a style tag will contain the contents of Style1-min.css. The IIS server, not ASP.NET, handles SSI.

SSI statement example

<style type="text/css"><!-- #include file="Style/Style1-min.css" --></style>

Differences. SSI is essentially a macro that can greatly ease development effort on our part. You can duplicate SSI with a web user control. But that is much bulkier and is likely much slower. Here we examine some differences.

I investigated SSI. Microsoft provides a solid foundation article. I learned that the file system cache on IIS can make SSI extremely fast, and that by bypassing managed code, it is hard to beat performance-wise.

Dynamically Include Files: microsoft.com

SSI differences

Lines of code:
SSI:             1
ASP.NET control: More than 20

Caching:
SSI:             File system cache on IIS7
ASP.NET control: Memory or output cache

Control tree:
SSI:             Literal controls added
ASP.NET control: Custom controls added

Assemblies:
SSI:             0
ASP.NET control: One assembly

Managed code:
SSI:             None
ASP.NET control: All

Styles. Minified style sheets are basically "compressed" CSS, which is important for performance of a site. I have shown the include before. This code shows how to insert a preprocessed style sheet into a style tag in HTML (an aspx file).

Inline style sheets

<%-- Style tags in an ASPX page's head element. --%>
<style type="text/css"><!-- #include file="Style/Style1-min.css" --></style>
<style type="text/css"><!-- #include file="Style/Style2-min.css" --></style>

Summary. We used SSI to optimize performance on both client and server. The example here results in a simpler control tree for ASP.NET. It will yield a smaller page for browsers that download the resource.

And: This enhances modularity. File-caching on IIS alleviates any overhead of SSI.