I was considering to add the HtmlValidator class to codeplex, but noticed that there are a few different implementations of HTML TidyLib for .Net. Not sure if any of them support my requirement to validate only structural errors, i.e. unmatched(not closed) open tags and unmatched(extra) close tags. But standard Tidy functionality will be good for most of users.
1. TidyManaged (https://github.com/markbeaton/TidyManaged)
Recent development (June 12, 2010), Positive reviews(e.g. here),Not much user activity in forums
Pro: Wrapper-easy upgrade to latest version of TidyLib.
Cons: As a wrapper it won't work in things like silverlight, and it requires you know the platform you'll be executing on at compile-time. Still, for many uses those restrictions aren't an issue.(reason from Eamon Nerbonne’s StackOverflow post)
2. TidyForNet (http://tidyfornet.sourceforge.net/ Wrapper for HTML Tidy and wvWare, using C# and interop.Release Date 2007-02-24
The same Pro& Cons for a wrapper Not much user activity
3. Tidynet.(http://tidynet.sourceforge.net/ )
A native .NET implementation -port from C.
Updated 2005-06-28,Not much user activity in forums
As not wrapper, opposite pro&cons: it will work on any .Net platform, but will not have any fixes from native TidyLib development.
4. A managed wrapper for the HTML Tidy library Code Project C++
Sample,how it can be done with single method implemented.
5. .NET Wrapper for HTML Tidy, based on a COM+ Wrapper for HTML Tidy