Reads up to the SerialPort.NewLine value in the input buffer.
The contents of the input buffer up to the first occurrence of a SerialPort.NewLine value.
Note that while this method does not return the SerialPort.NewLine value, the SerialPort.NewLine value is removed from the input buffer.
By default, the SerialPort.ReadLine method will block until a line is received. If this behavior is undesirable, set the SerialPort.ReadTimeout property to any non-zero value to force the SerialPort.ReadLine method to throw a TimeoutException if a line is not available on the port.
If it is necessary to switch between reading text and reading binary data from the stream, select a protocol that carefully defines the boundary between text and binary data, such as manually reading bytes and decoding the data.
Because the System.IO.Ports.SerialPort class buffers data, and the stream contained in the SerialPort.BaseStream property does not, the two might conflict about how many bytes are available to read. The SerialPort.BytesToRead property can indicate that there are bytes to read, but these bytes might not be accessible to the stream contained in the SerialPort.BaseStream property because they have been buffered to the System.IO.Ports.SerialPort class.