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TextReader.ReadLine Method


Reads a line of characters from the text reader and returns the data as a string.

 virtual System::String ^ ReadLine();
public virtual string ReadLine ();
public virtual string? ReadLine ();
abstract member ReadLine : unit -> string
override this.ReadLine : unit -> string
Public Overridable Function ReadLine () As String


The next line from the reader, or null if all characters have been read.


An I/O error occurs.

There is insufficient memory to allocate a buffer for the returned string.

The number of characters in the next line is larger than Int32.MaxValue


A line is defined as a sequence of characters followed by a carriage return (0x000d), a line feed (0x000a), a carriage return followed by a line feed, Environment.NewLine, or the end-of-stream marker. The string that is returned does not contain the terminating carriage return or line feed. The return value is null if the end of the input stream has been reached.

If the method throws an OutOfMemoryException exception, the reader's position in the underlying Stream is advanced by the number of characters the method was able to read, but the characters that were already read into the internal ReadLine buffer are discarded. Because the position of the reader in the stream cannot be changed, the characters that were already read are unrecoverable and can be accessed only by reinitializing the TextReader object. 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 TextReader class is an abstract class. Therefore, you do not instantiate it in your code. For an example of using the ReadLine method, see the StreamReader.ReadLine method.

Applies to

See also