Create logout for ASP.Net Web App

Create a new Razor Page called `logout`.

Go to the logoutModel code section (right click it in solution explorer and select goto PageModel).

Now change the `OnGet` method to this:

        public IActionResult OnGet()
        {
			HttpContext.Session.Clear();

			return LocalRedirect("/Index");
		}

Changing the `void` to `IActionResult` means this returns a page. The code will clear the current session which essentially will logout the user. Finally it redirects back to the index page.