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SerialPort.ReadExisting Method

Reads all immediately available bytes, based on the encoding, in both the stream and the input buffer of the SerialPort object.

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

public string ReadExisting()

Return Value

Type: System.String
The contents of the stream and the input buffer of the SerialPort object.

ExceptionCondition
InvalidOperationException

The specified port is not open.

This method returns the contents of the stream and internal buffer of the SerialPort object as a string. This method does not use a time-out. Note that this method can leave trailing lead bytes in the internal buffer, which makes the BytesToRead value greater than zero.

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.

NoteNote:

Because the SerialPort class buffers data, and the stream contained in the BaseStream property does not, the two might conflict about how many bytes are available to read. The BytesToRead property can indicate that there are bytes to read, but these bytes might not be accessible to the stream contained in the BaseStream property because they have been buffered to the SerialPort class.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

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

.NET Framework

Supported in: 3.5, 3.0, 2.0

.NET Compact Framework

Supported in: 3.5, 2.0
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