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SerialPort.Read Method (Char[], Int32, Int32)

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

Reads a number of bytes from the SerialPort input buffer and writes those bytes into a byte array at a given offset.

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

public int Read (
	char[] buffer,
	int offset,
	int count
public int Read (
	char[] buffer, 
	int offset, 
	int count
public function Read (
	buffer : char[], 
	offset : int, 
	count : int
) : int



The character array to write the input to.


The offset in the buffer array to begin writing.


The number of bytes to read.

Return Value

The number of bytes read.

Exception typeCondition


offset plus count is greater than the length of the buffer.

- or -

count is 1 and there is a surrogate character in the buffer.


The buffer passed is a null reference (Nothing in Visual Basic).


The offset or count parameters are outside a valid region of the buffer being passed. Either offset or count is less than zero.


The specified port is not open.


No bytes were available to read.

Use this method for reading bytes from the serial 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 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 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