How can I set the Last modified date in MVC3?

I have a MVC3 application. Google is looking at my web site but not indexing very much. Can you help me with a question I have.

I understand there's something called last modified date. I don't know if that is a meta tag or what it is. I have some web pages that are dynamic and some that are static. Should I be setting this tag somehow. What if 开发者_开发知识库it's a dynamic web page then how do I set that in MVC3.

I hope you can help

Thank you

Do some research on creating a Google Sitemap

http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=183668

Within each url in your sitemap you can define a <lastmod> element

<lastmod> Optional The date the URL was last modifed, in YYYY-MM-DDThh:mmTZD format (time value is optional).