Unity2019, c # 7.0

Use the SerialPort module to multi-threaded or asynchronously to monitor BytesToRead, is no problem to read, but I want to change to use method DataReceived event trigger type, hasn't been successful, however, tried various Settings are not, and finally found that when to read and write ReceivedBytesThreshold attribute, the runtime tip

NotImplementedException: The method or operation is not implemented.

If they are read, is pointing to the System. IO. Ports. SerialPort. Get_ReceivedBytesThreshold, if is set then pointing System. IO. Ports. SerialPort. Set_ReceivedBytesThreshold, doubt because it led to the ReceivedBytesThreshold actual operation of the property does not exist, so can't trigger events, does anyone know how can appear this situation, please?