StreamReader Class

Definition

public ref class StreamReader : System::IO::TextReader

public class StreamReader : System.IO.TextReader

[System.Serializable]public class StreamReader : System.IO.TextReader

[System.Serializable][System.Runtime.InteropServices.ComVisible(true)]public class StreamReader : System.IO.TextReader

type StreamReader = class    inherit TextReader

[<System.Serializable>]type StreamReader = class    inherit TextReader

[<System.Serializable>][<System.Runtime.InteropServices.ComVisible(true)>]type StreamReader = class    inherit TextReader

Public Class StreamReaderInherits TextReader

Inheritance

Object

TextReader

StreamReader

Inheritance

Object

MarshalByRefObject

TextReader

StreamReader

Attributes

SerializableAttributeComVisibleAttribute

Examples

The following example uses an instance ofStreamReader to read text from a file. The constructor used in this example is not supported for use in Windows Store Apps.

using System;using System.IO;class Test{    public static void Main()    {        try        {            // Create an instance of StreamReader to read from a file.            // The using statement also closes the StreamReader.            using (StreamReader sr = new StreamReader("TestFile.txt"))            {                string line;                // Read and display lines from the file until the end of                // the file is reached.                while ((line = sr.ReadLine()) != null)                {                    Console.WriteLine(line);                }            }        }        catch (Exception e)        {            // Let the user know what went wrong.            Console.WriteLine("The file could not be read:");            Console.WriteLine(e.Message);        }    }}

Imports System.IOClass Test    Public Shared Sub Main()        Try            ' Create an instance of StreamReader to read from a file.            Dim sr As StreamReader = New StreamReader("TestFile.txt")            Dim line As String            ' Read and display the lines from the file until the end             ' of the file is reached.            Do                line = sr.ReadLine()                Console.WriteLine(Line)            Loop Until line Is Nothing            sr.Close()        Catch E As Exception            ' Let the user know what went wrong.            Console.WriteLine("The file could not be read:")            Console.WriteLine(E.Message)        End Try    End SubEnd Class

The following example instantiates aStreamReader object and calls itsReadAsync method to read a file asynchronously.

using System;using System.IO;using System.Threading.Tasks;class Example{    static async Task Main()    {        await ReadAndDisplayFilesAsync();    }    static async Task ReadAndDisplayFilesAsync()    {        String filename = "TestFile1.txt";        Char[] buffer;        using (var sr = new StreamReader(filename)) {            buffer = new Char[(int)sr.BaseStream.Length];            await sr.ReadAsync(buffer, 0, (int)sr.BaseStream.Length);        }        Console.WriteLine(new String(buffer));    }}// The example displays the following output://       This is the first line of text in a relatively short file.//       This is the second line.//       This is the third line.//       This is the fourth and final line.

Imports System.IOImports System.Threading.TasksModule Example    Public Sub Main()        ReadAndDisplayFilesAsync()    End Sub    Private Async Sub ReadAndDisplayFilesAsync()        Dim filename As String = "TestFile1.txt"        Dim buffer() As Char                Using sr As New StreamReader(filename)            ReDim buffer(CInt(sr.BaseStream.Length))            Await sr.ReadAsync(buffer, 0, CInt(sr.BaseStream.Length))        End Using        Console.WriteLine(New String(buffer))    End SubEnd Module' The example displays the following output:'       This is the first line of text in a relatively short file.'       This is the second line.'       This is the third line.'       This is the fourth and final line.

Remarks

StreamReader is designed for character input in a particular encoding, whereas theStream class is designed for byte input and output. UseStreamReader for reading lines of information from a standard text file.

StreamReader defaults to UTF-8 encoding unless specified otherwise, instead of defaulting to the ANSI code page for the current system. UTF-8 handles Unicode characters correctly and provides consistent results on localized versions of the operating system. If you get the current character encoding using theCurrentEncoding property, the value is not reliable until after the firstRead method, since encoding auto detection is not done until the first call to aRead method.

By default, aStreamReader is not thread safe. SeeTextReader.Synchronized for a thread-safe wrapper.

TheRead(Char[], Int32, Int32) andWrite(Char[], Int32, Int32) method overloads read and write the number of characters specified by thecount parameter. These are to be distinguished fromBufferedStream.Read andBufferedStream.Write, which read and write the number of bytes specified by thecount parameter. Use theBufferedStream methods only for reading and writing an integral number of byte array elements.

For a list of common I/O tasks, seeCommon I/O Tasks.

See also

• Encoding
• Stream
• StreamWriter
• File and Stream I/O
• How to: Read Text from a File
• How to: Write Text to a File
• How to: Read and Write to a Newly Created Data File