Add an Option to set the Razor view location formats

[Eilon]

To customize the set of path formats that the Razor view engine will look at you need to customize the view engine itself. You need to either derive from RazorViewEngine, override the list of formats, and add that to the list of view engines, or you have to instantiate RazorViewEngine itself, set the list of formats, and add that to the list of view engines.

This is the property in question:

Mvc/src/Microsoft.AspNetCore.Mvc.Razor/RazorViewEngine.cs

Line 76 in af58c2e

public virtual IEnumerable<string> ViewLocationFormats { get; } = new[]

(Plus the one for areas.)

We already have a Razor View Options class (https://github.com/aspnet/Mvc/blob/af58c2e6b619697a1a57736e9e996bb4d7e6e7ee/src/Microsoft.AspNetCore.Mvc.Razor/RazorViewEngineOptions.cs) so we should have the default list of view location formats there instead.

[Eilon]

@rynowak for your FYI information this is the bug we talked about.

[dougbu]

@pranavkm didn't you remove ViewLocationFormats settability an age (just one age, not ages 😺) ago? What was the reasoning then?