Without await, the using statement can dispose the Stream before the
call to PutAsync completes, resulting in an ObjectDisposedException.
This fixes#4556.
The previous implementations resulted in an overload being hidden by one
without a default parameter, making it unclear which method was being
called. For example, consider the following signatures:
public MultipartItem(string content, string contenttype = null, string name = null, string filename = null)
public MultipartItem(string contenttype, string name = null, string filename = null)
From https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/named-and-optional-arguments,
> If two candidates are judged to be equally good, preference goes to a
> candidate that does not have optional parameters for which arguments
> were omitted in the call. This is a consequence of a general preference
> in overload resolution for candidates that have fewer parameters.
By changing to IEnumerable, it is possible to iterate only a portion of the list, which is useful when not all entries are needed (e.g., when testing a connection).
All existing backends have been updated, and any which were able to be changed to yield return results in a straightforward way now do.
Many backends had a try/catch in the List() method. Due to the fact that yield returns can't be placed within a try/catch block, these have been refactored to either scope the try/catch to the parts that (should) be the only places throwing exceptions, so that exceptions are still caught and handled.
Note that lazy evaluation may cause some changes in behavior - exceptions that were previously thrown at the point of invokation of List() may now be thrown while it is being enumerated.
I believe this will not be problematic though, as the only well-known exception seems to be FolderMissingException, which should be thrown by Test(), but TestList() attempts to enumerate the list to force this exception.
Any places that require the legacy behavior can get it by simply converting the lazy enumerable to a List()
Kenneth Skovhede