For which cases param could be of type string?
param
string
ServiceBusSender.SendMessagesAsync(new ServiceBusMessage(param)
EventHubProducerClient.SendAsync(new EventData(param))
None of the listed
QueueClient.SendAsync(new Message(param))
EventData and ServiceBusMessage support both string and byte[], Message is for byte[] only. Prefer byte[] for EventData.
EventData
ServiceBusMessage
byte[]
Message