private bool TryGetStreamingEnumerator(HubConnectionContext connection, string invocationId, ObjectMethodExecutor methodExecutor, object result, Type resultType, out IAsyncEnumerator <object> enumerator)
{
if (result != null)
{
// TODO: cache reflection for performance, on HubMethodDescriptor maybe?
resultType = UnwrapTask(resultType);
var observableInterface = IsIObservable(resultType) ?
resultType :
resultType.GetInterfaces().FirstOrDefault(IsIObservable);
if (observableInterface != null)
{
enumerator = AsyncEnumeratorAdapters.FromObservable(result, observableInterface, CreateCancellation());
return(true);
}
if (IsChannel(resultType, out var payloadType))
{
enumerator = AsyncEnumeratorAdapters.FromChannel(result, payloadType, CreateCancellation());
return(true);
}
}
enumerator = null;
return(false);
CancellationToken CreateCancellation()
{
var streamCts = new CancellationTokenSource();
connection.ActiveRequestCancellationSources.TryAdd(invocationId, streamCts);
return(CancellationTokenSource.CreateLinkedTokenSource(connection.ConnectionAbortedToken, streamCts.Token).Token);
}
}
private IAsyncEnumerator <object> GetStreamingEnumerator(HubConnectionContext connection, string invocationId, ObjectMethodExecutor methodExecutor, object result, Type resultType)
{
if (result != null)
{
var observableInterface = IsIObservable(resultType) ?
resultType :
resultType.GetInterfaces().FirstOrDefault(IsIObservable);
if (observableInterface != null)
{
return(AsyncEnumeratorAdapters.FromObservable(result, observableInterface, CreateCancellation()));
}
if (IsChannel(resultType, out var payloadType))
{
return(AsyncEnumeratorAdapters.FromChannel(result, payloadType, CreateCancellation()));
}
}
Log.InvalidReturnValueFromStreamingMethod(_logger, methodExecutor.MethodInfo.Name);
throw new InvalidOperationException($"The value returned by the streaming method '{methodExecutor.MethodInfo.Name}' is null, does not implement the IObservable<> interface or is not a ReadableChannel<>.");
CancellationToken CreateCancellation()
{
var streamCts = new CancellationTokenSource();
connection.ActiveRequestCancellationSources.TryAdd(invocationId, streamCts);
return(CancellationTokenSource.CreateLinkedTokenSource(connection.ConnectionAbortedToken, streamCts.Token).Token);
}
}
