Your ASP.NET hyperlink code will be translated to:
<a href="www.google.com">link</a>
If any link is not prefex with the symbol slash "/" or a scheme "https/http", the browser will append your provided link with current web folder path.
Example, this:
www.google.com
will become this:
http://www.yourwebsite.com/www.google.com
or this:
http://www.yourwebsite.com/member/www.google.com
It has nothing to with the Hyperlink server control in ASP.NET. It is the default behaviour of HTML.
Therefore, your have to prefix it with the scheme:
https
like this:
<asp:HyperLink ID="hp1" runat="server" NavigateUrl="https://www.google.com">Link</asp:HyperLink>