Using PartitionedSender to send an event to an EventHub got exception.

var manager = NamespaceManager.CreateFromConnectionString(xxx);
var eventHubSender = eventHubClient.CreatePartitionedSender(description.PartitionIds[0]);

eventHubSender.Send(new EventData("Hello") {PartitionKey=eventHubSender.PartitionId);

result in

$exception{"The specified partition key '0' is invalid for partition '0'. Do not set a value for partition key or send using EventHubClient.Send."}System.Exception {System.ArgumentException}

What is wrong?