You can tell from the url if the view is on a site, so I'm not sure why you would need to query for it? For your example url, the view is on the default site - because no site is specified. If it was on a different site, your site url would be like this:
I have a dot net application which receives the share URL of a visualization as an input. I want to be able to validate the input URL to check if it is a valid URL and exists in the Tableau Server.
true. (The view represented by the share URL actually exists in the default site in Tableau)
false. (No such view exists in the default site in Tableau)