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SerialPort.CDHolding Property

Note: This property is new in the .NET Framework version 2.0.

Gets the state of the Carrier Detect line for the port.

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

public bool CDHolding { get; }
/** @property */
public boolean get_CDHolding ()

public function get CDHolding () : boolean

Property Value

true if the carrier is detected; otherwise, false.

Exception typeCondition


The port is in an invalid state.

- or -

An attempt to set the state of the underlying port failed. For example, the parameters passed from this SerialPort object were invalid.


The stream is closed. This can occur because the Open method has not been called or the Close method has been called.

This property can be used to monitor the state of the carrier detection line for a port. No carrier usually indicates that the receiver has hung up and the carrier has been dropped.

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0

.NET Compact Framework

Supported in: 2.0