ReadLine Method

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

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

public virtual string ReadLine()

Return Value

Type: System..::..String
The next line from the reader, or nullNothingnullptrunita null reference (Nothing in Visual Basic) if all characters have been read.

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 nullNothingnullptrunita null reference (Nothing in Visual Basic) 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.