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SerialPort.ReadTo Method

Reads a string up to the specified value in the input buffer.

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

public string ReadTo (
	string value
public String ReadTo (
	String value
public function ReadTo (
	value : String
) : String
Not applicable.



A value that indicates where the read operation stops.

Return Value

The contents of the input buffer up to the specified value.

Exception typeCondition


The length of the value parameter is 0.


The value parameter is a null reference (Nothing in Visual Basic).


The specified port is not open.


The operation did not complete before the time-out period ended.

This method reads a string up to the specified value. While the returned string does not include the value, the value is removed from the input buffer.

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 Server 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 Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

.NET Compact Framework

Supported in: 2.0