StreamReader

StreamReader is a class in the .NET framework and .NET Core under the System.IO namespace. It provides a convenient way to read characters from a byte stream by decoding bytes into text using a specified character encoding. StreamReader buffers input to improve performance and is commonly used to read text from files, network streams, or memory streams.

Constructing a StreamReader can be done from a Stream or from a file path. Overloads allow specifying the encoding, whether to detect encoding from a byte order mark (BOM), buffer size, and whether to leave the underlying stream open when the reader is disposed. The CurrentEncoding property reveals the encoding in use, and the BaseStream property exposes the underlying stream. By default, disposal of a StreamReader closes the underlying stream, unless you opt to leave it open.

Key reading operations include Read, Read(char[], int, int), ReadLine, and ReadToEnd, which provide character-by-character, block, line-based, or complete-file reads respectively. Asynchronous variants—ReadAsync, ReadLineAsync, and ReadToEndAsync—enable non-blocking I/O in applications that require responsiveness or scalable I/O. The EndOfStream property indicates when the end of the underlying stream has been reached.

StreamReader is widely used in file I/O and text-processing scenarios, and is compatible with various stream sources, including FileStream, MemoryStream, and network streams. It remains a staple for developers needing robust, encoding-aware text reading. In other programming environments, similar concepts exist, such as Java’s InputStreamReader and Python’s text I/O wrappers, but StreamReader specifically refers to the .NET implementation.