Not authorize tag helper addition

[mute503]

For the authorize tag helpers, a typical case that I didn't see covered would be needing to show one section of html to authorized users and show a different section of html to non-authorized users. Maybe something like a asp-authorize-anonymous.

I didn't see a way of doing this with current tag helpers but it could be useful and effectively eliminate if-elses in razor based on user being logged in.

[dpaquette]

This is actually a pretty common scenario but I'm not sure how best to solve for it. I am open to suggestions.
Here are a couple options I am kicking around:

Introducing an authorize tag

<authorize asp-policy="somePolicy">
  <authorized> <div> this will only be rendered if the user is authorized </div> </authorized>
  <not-authorized> <div> this will only be rendered if the user is not authorized </div> </not-authorized>
</authorize>

This one is a little verbose but should be pretty clear what is happening.

Introducing an asp-not-authorize attribute

<div asp-authorize asp-policy="somePolicy"> this will only be rendered if the user is authorized </div> 
<div asp-not-authorize asp-policy="somePolicy"> this will only be rendered if the user is not authorized </div> 

This one is less verbose than the first option but it would require the policy to be evaluated twice which seems like a bad idea.