obtain generic enumerator from an array

Question

In C#, how does one obtain a generic enumerator from a given array?

In the code below, MyArray is an array of MyType objects. I\'d like to

Answer 1

You can decide for yourself whether casting is ugly enough to warrant an extraneous library call:

int[] arr;
IEnumerator Get1()
{
    return ((IEnumerable)arr).GetEnumerator();  // <-- 1 non-local call

    // ldarg.0 
    // ldfld int32[] foo::arr
    // castclass System.Collections.Generic.IEnumerable`1
    // callvirt instance class System.Collections.Generic.IEnumerator`1 System.Collections.Generic.IEnumerable`1::GetEnumerator()
}

IEnumerator Get2()
{
    return arr.AsEnumerable().GetEnumerator();   // <-- 2 non-local calls

    // ldarg.0 
    // ldfld int32[] foo::arr
    // call class System.Collections.Generic.IEnumerable`1 System.Linq.Enumerable::AsEnumerable(class System.Collections.Generic.IEnumerable`1)
    // callvirt instance class System.Collections.Generic.IEnumerator`1 System.Collections.Generic.IEnumerable`1::GetEnumerator()
}

And for completeness, one should also note that the following is not correct--and will crash at runtime--because T[] chooses the non-generic IEnumerable interface for its default (i.e. non-explicit) implementation of GetEnumerator().

IEnumerator NoGet()                    // error - do not use
{
    return (IEnumerator)arr.GetEnumerator();

    // ldarg.0 
    // ldfld int32[] foo::arr
    // callvirt instance class System.Collections.IEnumerator System.Array::GetEnumerator()
    // castclass System.Collections.Generic.IEnumerator`1
}

The mystery is, why doesn't SZGenericArrayEnumerator inherit from SZArrayEnumerator--an internal class which is currently marked 'sealed'--since this would allow the (covariant) generic enumerator to be returned by default?