StreamReader Class

Definition

Namespace:

System.IO

Assembly:

System.Runtime.dll

Source:

StreamReader.cs

Implements a TextReader that reads characters from a byte stream in a particular encoding.

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

public class StreamReader : System.IO.TextReader

type StreamReader = class
    inherit TextReader

Public Class StreamReader
Inherits TextReader

Inheritance

Object

MarshalByRefObject

TextReader

StreamReader

Examples

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

using namespace System;
using namespace System::IO;
int main()
{
   try
   {
      // Create an instance of StreamReader to read from a file.
      StreamReader^ sr = gcnew StreamReader( "TestFile.txt" );
      try
      {
         String^ line;
         
         // Read and display lines from the file until the end of 
         // the file is reached.
         while ( line = sr->ReadLine() )
         {
            Console::WriteLine( line );
         }
      }
      finally
      {
         if ( sr )
            delete (IDisposable^)sr;
      }
   }
   catch ( Exception^ e ) 
   {
      // Let the user know what went wrong.
      Console::WriteLine( "The file could not be read:" );
      Console::WriteLine( e->Message );
   }
}

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.IO

Class 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 Sub
End Class

The following example instantiates a StreamReader object and calls its ReadAsync 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.IO
Imports System.Threading.Tasks

Module 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 Sub
End 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 the Stream class is designed for byte input and output. Use StreamReader for reading lines of information from a standard text file.

Important

This type implements the IDisposable interface. When you have finished using the type, you should dispose of it either directly or indirectly. To dispose of the type directly, call its Dispose method in a try/catch block. To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). For more information, see the "Using an Object that Implements IDisposable" section in the IDisposable interface topic.

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 the CurrentEncoding property, the value is not reliable until after the first Read method, since encoding auto detection is not done until the first call to a Read method.

By default, a StreamReader is not thread safe. See TextReader.Synchronized for a thread-safe wrapper.

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

Note

When reading from a Stream, it is more efficient to use a buffer that is the same size as the internal buffer of the stream.

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

Constructors

StreamReader(Stream, Boolean)	Initializes a new instance of the StreamReader class for the specified stream, with the specified byte order mark detection option.
StreamReader(Stream, Encoding, Boolean, Int32, Boolean)	Initializes a new instance of the StreamReader class for the specified stream based on the specified character encoding, byte order mark detection option, and buffer size, and optionally leaves the stream open.
StreamReader(Stream, Encoding, Boolean, Int32)	Initializes a new instance of the StreamReader class for the specified stream, with the specified character encoding, byte order mark detection option, and buffer size.
StreamReader(Stream, Encoding, Boolean)	Initializes a new instance of the StreamReader class for the specified stream, with the specified character encoding and byte order mark detection option.
StreamReader(Stream, Encoding)	Initializes a new instance of the StreamReader class for the specified stream, with the specified character encoding.
StreamReader(Stream)	Initializes a new instance of the StreamReader class for the specified stream.
StreamReader(String, Boolean)	Initializes a new instance of the StreamReader class for the specified file name, with the specified byte order mark detection option.
StreamReader(String, Encoding, Boolean, FileStreamOptions)	Initializes a new instance of the StreamReader class for the specified file path, with the specified character encoding, byte order mark detection option, and configured with the specified FileStreamOptions object.
StreamReader(String, Encoding, Boolean, Int32)	Initializes a new instance of the StreamReader class for the specified file name, with the specified character encoding, byte order mark detection option, and buffer size.
StreamReader(String, Encoding, Boolean)	Initializes a new instance of the StreamReader class for the specified file name, with the specified character encoding and byte order mark detection option.
StreamReader(String, Encoding)	Initializes a new instance of the StreamReader class for the specified file name, with the specified character encoding.
StreamReader(String, FileStreamOptions)	Initializes a new instance of the StreamReader class for the specified file path, using the default encoding, enabling detection of byte order marks at the beginning of the file, and configured with the specified FileStreamOptions object.
StreamReader(String)	Initializes a new instance of the StreamReader class for the specified file name.

Fields

Null	A StreamReader object around an empty stream.

Properties

BaseStream	Returns the underlying stream.
CurrentEncoding	Gets the current character encoding that the current StreamReader object is using.
EndOfStream	Gets a value that indicates whether the current stream position is at the end of the stream.

Methods

Close()	Closes the StreamReader object and the underlying stream, and releases any system resources associated with the reader.
CreateObjRef(Type)	Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object. (Inherited from MarshalByRefObject)
DiscardBufferedData()	Clears the internal buffer.
Dispose()	Releases all resources used by the TextReader object. (Inherited from TextReader)
Dispose(Boolean)	Closes the underlying stream, releases the unmanaged resources used by the StreamReader, and optionally releases the managed resources.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetLifetimeService()	Obsolete. Retrieves the current lifetime service object that controls the lifetime policy for this instance. (Inherited from MarshalByRefObject)
GetType()	Gets the Type of the current instance. (Inherited from Object)
InitializeLifetimeService()	Obsolete. Obtains a lifetime service object to control the lifetime policy for this instance. (Inherited from MarshalByRefObject)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
MemberwiseClone(Boolean)	Creates a shallow copy of the current MarshalByRefObject object. (Inherited from MarshalByRefObject)
Peek()	Returns the next available character but does not consume it.
Read()	Reads the next character from the input stream and advances the character position by one character.
Read(Char[], Int32, Int32)	Reads a specified maximum of characters from the current stream into a buffer, beginning at the specified index.
Read(Span<Char>)	Reads the characters from the current stream into a span.
ReadAsync(Char[], Int32, Int32)	Reads a specified maximum number of characters from the current stream asynchronously and writes the data to a buffer, beginning at the specified index.
ReadAsync(Memory<Char>, CancellationToken)	Asynchronously reads the characters from the current stream into a memory block.
ReadBlock(Char[], Int32, Int32)	Reads a specified maximum number of characters from the current stream and writes the data to a buffer, beginning at the specified index.
ReadBlock(Span<Char>)	Reads the characters from the current stream and writes the data to a buffer.
ReadBlockAsync(Char[], Int32, Int32)	Reads a specified maximum number of characters from the current stream asynchronously and writes the data to a buffer, beginning at the specified index.
ReadBlockAsync(Memory<Char>, CancellationToken)	Asynchronously reads the characters from the current stream and writes the data to a buffer.
ReadLine()	Reads a line of characters from the current stream and returns the data as a string.
ReadLineAsync()	Reads a line of characters asynchronously from the current stream and returns the data as a string.
ReadLineAsync(CancellationToken)	Reads a line of characters asynchronously from the current stream and returns the data as a string.
ReadToEnd()	Reads all characters from the current position to the end of the stream.
ReadToEndAsync()	Reads all characters from the current position to the end of the stream asynchronously and returns them as one string.
ReadToEndAsync(CancellationToken)	Reads all characters from the current position to the end of the stream asynchronously and returns them as one string.
ToString()	Returns a string that represents the current object. (Inherited from Object)

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