Commenting

ASP.NET supports a little known feature called “server-side comments” that you can use to completely disable code/controls/html in a page.  Server-side comments in ASP.NET are delimited using a <%-- --%> syntax.  For example:

        <%--

            Commented out HTML/CODE/Markup.  Anything with

            this block will not be parsed/handled by ASP.NET.

            <%# Eval(“SomeProperty”) %>     

        --%>

One common question people ask is what the difference is between using client-side HTML comments and server-side comments.  The key difference is that with client-side comments it is the browser which is ignoring the content within them.  Code/controls within client-side comments will still be executed on the server and sent down to the browser.  As such, if there is a server error caused within them it will block running the page.

With server-side comments, the ASP.NET compiler ignores everything within these blocks at parse/compile time, and removes the content completely when assembling the page (like its contents weren’t there at all).  Consequently, any errors caused by mal-formed controls or issues with inline code or data-binding expressions within them will be ignored.  The page is also just as fast with controls/code within server-side comments as if there were no controls/code on the page at all (there is no runtime performance overhead to them).