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TextReader.ReadLine Method

Reads a line of characters from the current stream and returns the data as a string.

[Visual Basic]
Public Overridable Function ReadLine() As String
[C#]
public virtual string ReadLine();
[C++]
public: virtual String* ReadLine();
[JScript]
public function ReadLine() : String;

Return Value

The next line from the input stream, or a null reference (Nothing in Visual Basic) if all characters have been read.

Exceptions

Exception Type Condition
IOException An I/O error occurs.
OutOfMemoryException There is insufficient memory to allocate a buffer for the returned string.
ObjectDisposedException The TextReader is closed.
ArgumentOutOfRangeException The number of characters in the next line is larger than MaxValue

Remarks

A line is defined as a sequence of characters followed by a carriage return (0x000d), a line feed (0x000a), Environment.NewLine, or the end of stream marker. The string that is returned does not contain the terminating carriage return and/or line feed. The returned value is a null reference (Nothing in Visual Basic) if the end of the input stream has been reached.

If the current method throws an OutOfMemoryException, the reader's position in the underlying Stream is advanced by the number of characters the method was able to read, but the characters already read into the internal ReadLine buffer are discarded. Since the position of the reader in the stream cannot be changed, the characters already read are unrecoverable, and can be accessed only by reinitializing the TextReader. If the initial position within the stream is unknown or the stream does not support seeking, the underlying Stream also needs to be reinitialized.

To avoid such a situation and produce robust code you should use the Read method and store the read characters in a preallocated buffer.

The following table lists examples of other typical or related I/O tasks.

To do this... See the example in this topic...
Create a text file. Writing Text to a File
Write to a text file. Writing Text to a File
Read from a text file. Reading Text from a File
Append text to a file. Opening and Appending to a Log File

File.AppendText

FileInfo.AppendText

Get the size of a file. FileInfo.Length
Get the attributes of a file. File.GetAttributes
Set the attributes of a file. File.SetAttributes
Determine if a file exists. File.Exists
Read from a binary file. Reading and Writing to a Newly Created Data File
Write to a binary file. Reading and Writing to a Newly Created Data File

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard

See Also

TextReader Class | TextReader Members | System.IO Namespace | Working with I/O | Reading Text from a File | Writing Text to a File

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