Yes.
In windows, the serial port is buffered so there will be a delay before the data is passed to your application.
It is also possible to designate an event character on the port. When the serial port receives a byte matching the event character - it stops waiting and returns any buffered data to the application.
A typical event character is line feed eg. '\n'.
If the Arduino is programmed to send messages terminated with a line feed - the data will appear promptly in your application.
https://msdn.microsoft.com/en-us/library/system.io.ports.serialport%28v=vs.110%29.aspx[
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