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SerialPort.WriteLine Method (String)


Writes the specified string and the NewLine value to the output buffer.

Namespace:   System.IO.Ports
Assembly:  System (in System.dll)

public void WriteLine(
	string text


Type: System.String

The string to write to the output buffer.

Exception Condition

The str parameter is null.


The specified port is not open.


The WriteLine method could not write to the stream.

If there are too many bytes in the input buffer and Handshake is set to XOnXOff then the SerialPort object may raise a TimeoutException while it waits for the device to be ready to accept more data.

The written output includes the NewLine string.

The following code example demonstrates the use of the SerialPort class to allow two users to chat from two separate computers connected by a null modem cable. This code example is part of a larger code example provided for the SerialPort class.

public static void Main()
    string name;
    string message;
    StringComparer stringComparer = StringComparer.OrdinalIgnoreCase;
    Thread readThread = new Thread(Read);

    // Create a new SerialPort object with default settings.
    _serialPort = new SerialPort();

    // Allow the user to set the appropriate properties.
    _serialPort.PortName = SetPortName(_serialPort.PortName);
    _serialPort.BaudRate = SetPortBaudRate(_serialPort.BaudRate);
    _serialPort.Parity = SetPortParity(_serialPort.Parity);
    _serialPort.DataBits = SetPortDataBits(_serialPort.DataBits);
    _serialPort.StopBits = SetPortStopBits(_serialPort.StopBits);
    _serialPort.Handshake = SetPortHandshake(_serialPort.Handshake);

    // Set the read/write timeouts
    _serialPort.ReadTimeout = 500;
    _serialPort.WriteTimeout = 500;

    _continue = true;

    Console.Write("Name: ");
    name = Console.ReadLine();

    Console.WriteLine("Type QUIT to exit");

    while (_continue)
        message = Console.ReadLine();

        if (stringComparer.Equals("quit", message))
            _continue = false;
                String.Format("<{0}>: {1}", name, message));


public static void Read()
    while (_continue)
            string message = _serialPort.ReadLine();
        catch (TimeoutException) { }

.NET Framework
Available since 2.0
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