how to make trial version of win and web application in .Net technology

The usual way is a registry key, or set of same. You keep track of the install date, and once it's passed without the user entering a key, you set a flag saying the time's up. You could also track individual uses; after 30 "starts" it gets locked (preventing workarounds involving changing the system time). A knowledgeable person can always hack such an implementation because they can access and edit their registry, but it'll keep 95% of your users honest.

The most foolproof way requires a web service, which means the app requires an Internet connection to run (no problem if it does anyway, but you might have trouble convincing your users that a notepad app need internet access). The app will call the service on installation to say it's been installed on the current date with a given license key (or a default "trial" key) and ask for a GUID identifying the installation. Then, each startup, it will ask another service if it's allowed to run. If you expect your app to be popular, you'll need some serious hardware behind the scenes as the service will be hit every time any installation starts up.