This is the asynchronous version of System.Data.Common.DbDataReader.Read. Providers should override with an appropriate implementation. The cancellationToken may optionally be ignored. The default implementation invokes the synchronous System.Data.Common.DbDataReader.Read method and returns a completed task, blocking the calling thread. The default implementation will return a cancelled task if passed an already cancelled cancellationToken. Exceptions thrown by Read will be communicated via the returned Task Exception property. Do not invoke other methods and properties of the DbDataReader object until the returned Task is complete. Advances the reader to the next record in a result set.