Question

if a page contains a Viewstate in the source. Does this mean the webpage is using ASP.NET WebForms or could this also be an MVC project ?

Thanks!

Answer 1

Source: ASP.NET MVC and Web Forms Integration

IIS needs to be able to figure out whether a given request is an
ASP.NET MVC or a Web Forms request. Once it can figure that out, IIS
can send the request to the appropriate handler and the application
behaves as you’d expect.

check these lines from that nice article.

Caution

Watch out for ViewState! Though many parts of the ASP.NET Framework
are accessible by both Web Forms and ASP.NET MVC, the most significant
piece of the Web Forms Framework that is not supported in ASP.NET MVC
at all is ViewState. Most often, ViewState is used for a Web Forms
Page to communicate with itself, so the chances of running into
ViewState issues when cross-posting between Web Forms pages and
ASP.NET MVC controllers are slim.

However, when transitioning your Web Forms application to ASP.NET MVC,
be on the lookout for any code in your Web Forms application that
expects ViewState — the ViewState data will not exist during the
course of an ASP.NET MVC request so code that depends on it will
likely break!