Converting Array to IEnumerable

Question

To my surprise, I get the following statement:

public static IEnumerable AllEnums 
  => Enum.GetValues(typeof(SomeType));

to

Answer 1

The general Array base class is not typed, so it does not implement any type-specific interfaces; however, a vector can be cast directly - and GetValues actually returns a vector; so:

public static IEnumerable<SomeType> AllEnums
    = (SomeType[])Enum.GetValues(typeof(SomeType));

or perhaps simpler:

public static SomeType[] AllEnums 
    = (SomeType[])Enum.GetValues(typeof(SomeType));

Answer 2

I thought that the latter was inheriting from the former.

Enum.GetValues returns Array, which implements the non-generic IEnumerable, so you need to add a cast:

public static IEnumerable<SomeType> AllEnums = Enum.GetValues(typeof(SomeType))
    .Cast<SomeType>()
    .ToList(); 

This works with LINQ because Cast<T> extension method is defined for the non-generic IEnumerable interface, not only on IEnumerable<U>.

Edit: A call of ToList() avoid inefficiency associated with walking multiple times an IEnumerable<T> produced by LINQ methods with deferred execution. Thanks, Marc, for a great comment!