Handle third party library class depedency which do not have interface

Question

I am working on EWS. A class is made to query mail box and read emails.

public class MailReader
{
 private readonly ExchangeService _service;
 private readonly PropertySet _propertySet;
 private readonly IFolderSearch _folder;
 private readonly IMailAttachmentAdapter _attachment;
 private const int MaxEmail = 1000; 
 public MailReader(
 ExchangeService service,
 PropertySet propertySet,
 IFolderSearch folder,
 IMailAttachmentAdapter attachment)
 {
 _service = service;
 _folder = folder;
 _propertySet = propertySet;
 _attachment = attachment;
 }

what is the best way to inject ExchangeService , PropertySet classes are sealed and with no interface. Planning to use AutoFac for dependency management.

any pointers will be helpful.

• JacquesB: If you don't need to substitute these dependencies, then injecting the concrete classes like you do seem fine.
• Christian Sauer: I would hit the vendor with a club, a big one. Who does distribute concrete classes with no interface in 2018? The 80s have called...
• S.D.: Create the interface yourself, has the added benefit of decoupling.

Answer 1

One of the simplest, but long-winded, ways to solve this is to use the delegation pattern:

interface IDelegatedExchangeService
{
 bool AcceptGzipEncoding { get; set; }
 string ClientRequestId { get; set; }
 ...
}
class ConcreteExchangeService : IDelegatedExchangeService
{
 private ExchangeService _exchangeService;
 public bool AcceptGzipEncoding
 {
 get => _exchangeService.AcceptGzipEncoding;
 set => _exchangeService.AcceptGzipEncoding = value;
 }
 ...
}

and to then use IDelegatedExchangeService throughout your code.