I have noticed that in all the examples and tutorials on ASP.Net 5 (core) I have seen from Microsoft and the default Web Application template in VS 2015 use @ViewData["XXX"] instead of @ViewBag.XXX. Is this the, now, recommended way of passing data up from the controller instead of ViewBag? I know that ViewBag is a wrapper for ViewData but in the old tutorials (ASP.NET 4.5) they use ViewBag. If they are now encouraging developers to use ViewData why the change?
Both are still valid. There is no specific guidance on the docs.asp.net github project. Although there is this discussion on docs.asp.net issues.
That links through to a comment from one the product team which says:
"Since ViewData (Dictionary) look-ups far out-perform ViewBag (dynamic) invocations, the last is probably the best choice."
So I'd say it purely a style choice based upon the fact that ViewData performs better.
来源：https://stackoverflow.com/questions/34635874/is-viewdata-the-new-standard-over-viewbag-for-asp-net-5-core