If you look at the definition for
foreach (in C# Reference)[
^]:
The foreach statement repeats a group of embedded statements for each element in an array or an object collection that implements the System.Collections.IEnumerable or System.Collections.Generic.IEnumerable<T> interface. The foreach statement is used to iterate through the collection to get the information that you want, but can not be used to add or remove items from the source collection to avoid unpredictable side effects. If you need to add or remove items from the source collection, use a for loop.
Without any more information on the object being called and based on the information above, I would conclude that the
System.Collections.IEnumerable
or
System.Collections.Generic.IEnumerable<T>
interface is not implemented for C#.