I declared all meta property available by social cards in my c# website made on Sitecore using [https://moz.com/blog/meta-data-templates-123/]
Included tags like for ex:
meta name="twitter:card" content="summary"
meta name="twitter:site" content="website"
meta name="twitter:creator" content="content"
Validator [https://cards-dev.twitter.com/validator] is approving my cards and showing me required image, text and URL. But twitter buttons in my social sharing module are not fetching data from these meta tags. Kindly suggest
Sounds to me like Twitter can't see your website. The Twitter share button does not send information to Twitter except from the sharing url, normally the Url of the page. Then Twitter will crawl that Url to get the Twitter card tags and any other information required to expand the url in the tweet.
If your Site is not public, e.g. a local dev site or demo site behind a VPN, twitter will not be able to expand the url properly.