public Task Close()
{
var taskCompletionSource = new TaskCompletionSource <bool>();
if (_client.State == CommunicationState.Closed || _client.State == CommunicationState.Closing)
{
taskCompletionSource.TrySetResult(false);
}
else
{
_client.CloseAsync(taskCompletionSource);
}
return(taskCompletionSource.Task);
}