We checked more carefully again:
result for CSHTML5 beta 9.0 build /errors:
.NET 4.5: ok, works as expected
.NET 4.5.1: ok, works as expected
.NET 4.5.2: ok, works as expected
.NET 4.6: error: method "Array.Empty" is not yet supported
.NET 4.6.1: error: method "Array.Empty" is not yet supported
.NET 4.6.2: error: method "Array.Empty" is not yet supported
Probably I made a mistake in my first message : we are not upgraded from .NET 4.6
.1, but we upgraded from .NET 4.5
The good news: we should revitalize of broken projects by set it back to .NET 4.5.2. !
Anyway, the problem exist, (even if we change WCF collection settings manually/advanced mode from Array to ObservableCollection both Server and Client side): max. 4.5.2 , if you want any 4.6.X : you got "Array.Empty" build errors.
So, any official help/statement from CSHTML5 side?
Thanks in advance,