Artículo
11/18/2011

StreamReader Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

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

Inheritance Hierarchy

System.Object
System.IO.TextReader
System.IO.StreamReader

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

Syntax

'Declaration
<ComVisibleAttribute(True)> _
Public Class StreamReader _
    Inherits TextReader

[ComVisibleAttribute(true)]
public class StreamReader : TextReader

The StreamReader type exposes the following members.

Constructors

	Name	Description
	StreamReader(Stream)	Initializes a new instance of the StreamReader class for the specified stream.
	StreamReader(String)	When it is called by trusted applications, initializes a new instance of the StreamReader class for the specified file name.
	StreamReader(Stream, Boolean)	Initializes a new instance of the StreamReader class for the specified stream, using the specified byte order mark detection option.
	StreamReader(Stream, Encoding)	Initializes a new instance of the StreamReader class for the specified stream, using the specified character encoding.
	StreamReader(String, Boolean)	When it is called by trusted applications, initializes a new instance of the StreamReader class for the specified file name, using the specified byte order mark detection option.
	StreamReader(String, Encoding)	When it is called by trusted applications, initializes a new instance of the StreamReader class for the specified file name, using the specified character encoding.
	StreamReader(Stream, Encoding, Boolean)	Initializes a new instance of the StreamReader class for the specified stream, using the specified character encoding and byte order mark detection option.
	StreamReader(String, Encoding, Boolean)	When it is called by trusted applications, initializes a new instance of the StreamReader class for the specified file name, using the specified character encoding and byte order mark detection option.
	StreamReader(Stream, Encoding, Boolean, Int32)	Initializes a new instance of the StreamReader class for the specified stream, using the specified character encoding, byte order mark detection option, and buffer size.
	StreamReader(String, Encoding, Boolean, Int32)	When it is called by trusted applications, initializes a new instance of the StreamReader class for the specified file name, using the specified character encoding, byte order mark detection option, and buffer size.

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Properties

	Name	Description
	BaseStream	When it is called by trusted applications, returns the underlying stream.
	CurrentEncoding	When it is called by trusted applications, gets the current character encoding that the current StreamReader object is using.
	EndOfStream	When it is called by trusted applications, gets a value that indicates whether the current stream position is at the end of the stream.

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Methods

	Name	Description
	Close	When it is called by trusted applications, closes the StreamReader object and the underlying stream, and releases any system resources associated with the reader. (Overrides TextReader.Close().)
	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. (Overrides TextReader.Dispose(Boolean).)
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	Peek	When it is called by trusted application, returns the next available character but does not consume it. (Overrides TextReader.Peek().)
	Read()	When it is called by trusted applications, reads the next character from the input stream and advances the character position by one character. (Overrides TextReader.Read().)
	Read(array<Char[], Int32, Int32)	When it is called by trusted applications, reads a maximum of count characters from the current stream into buffer, beginning at index. (Overrides TextReader.Read(array<Char[], Int32, Int32).)
	ReadBlock	(Overrides TextReader.ReadBlock(array<Char[], Int32, Int32).) In Silverlight for Windows Phone Windows Phone OS 7.1, this member is inherited from TextReader.ReadBlock(array<Char[], Int32, Int32). In XNA Framework Xbox 360, this member is inherited from TextReader.ReadBlock(array<Char[], Int32, Int32).
	ReadLine	When it is called by trusted applications, reads a line of characters from the current stream and returns the data as a string. (Overrides TextReader.ReadLine().)
	ReadToEnd	When it is called by trusted applications, reads the stream from the current position to the end of the stream. (Overrides TextReader.ReadToEnd().)
	ToString	Returns a string that represents the current object. (Inherited from Object.)

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Fields

	Name	Description
	Null	A StreamReader object around an empty stream.

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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.

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.

By default, a StreamReader is not thread safe.

The Read(array<Char[], Int32, Int32) and Write(array<Char[], Int32, Int32) method overloads read and write the number of characters specified by the count parameter.

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.

Examples

The following example uses a StreamReader object in a trusted application that runs outside the browser. The StreamReader object reads the contents of a file the user's My Documents folder, and displays the contents in a text box control (named inputData).

For an example of how to save the contents of a file, see the StreamWriter class.

For example code and information about how to create an application that runs outside the browser, see Out-of-Browser Support.

Private Sub OpenFile_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)

    If Application.Current.HasElevatedPermissions Then
    
        ' fileLoc is a global string variable.
        fileLoc = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "MyDoc.txt")

        ' Create the file if it does not exist.
        If Not File.Exists(fileLoc) Then
            Using swNew As New StreamWriter(fileLoc)
                swNew.WriteLine("Sample text")
            End Using
        End If

        ' Display the contents in a TextBox.
        Using sr As New StreamReader(fileLoc)
            inputData.Text = sr.ReadToEnd()
            inputData.Visibility = Visibility.Visible
        End Using
    End If
End Sub

private void OpenFile_Click(object sender, RoutedEventArgs e)
{

    if (Application.Current.HasElevatedPermissions)
    {
        // fileLoc is a global string variable.
        fileLoc = System.IO.Path.Combine(Environment.GetFolderPath(
           Environment.SpecialFolder.MyDocuments), "MyDoc.txt");

        // Create the file if it does not exist.
        if (!File.Exists(fileLoc))
        {
            using (StreamWriter swNew = new StreamWriter(fileLoc))
            {
                swNew.WriteLine("Sample text");
            }
        }

        // Display the contents in a TextBox.
        using (StreamReader sr = new StreamReader(fileLoc))
        {
            inputData.Text = sr.ReadToEnd();
            inputData.Visibility = Visibility.Visible;
        }
    }
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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