FileStream Class

Definition

Namespace:: System.IO

Assemblies:: mscorlib.dll, System.IO.FileSystem.dll

Assemblies:: netstandard.dll, System.Runtime.dll

Assembly:: System.IO.FileSystem.dll

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: FileStream.cs

Source:: FileStream.cs

Source:: FileStream.cs

Source:: FileStream.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Provides aStream for a file, supporting both synchronous and asynchronous read and write operations.

public ref class FileStream : System::IO::Stream

public class FileStream : System.IO.Stream

[System.Runtime.InteropServices.ComVisible(true)]public class FileStream : System.IO.Stream

type FileStream = class    inherit Stream

[<System.Runtime.InteropServices.ComVisible(true)>]type FileStream = class    inherit Stream

Public Class FileStreamInherits Stream

Inheritance: Object
Stream
FileStream

Inheritance: Object
MarshalByRefObject
Stream
FileStream

Derived: System.IO.IsolatedStorage.IsolatedStorageFileStream

Attributes: ComVisibleAttribute

Examples

The following example demonstrates some of theFileStream constructors.

using System;using System.IO;using System.Text;class Test{    public static void Main()    {        string path = @"c:\temp\MyTest.txt";        // Delete the file if it exists.        if (File.Exists(path))        {            File.Delete(path);        }        //Create the file.        using (FileStream fs = File.Create(path))        {            AddText(fs, "This is some text");            AddText(fs, "This is some more text,");            AddText(fs, "\r\nand this is on a new line");            AddText(fs, "\r\n\r\nThe following is a subset of characters:\r\n");            for (int i=1;i < 120;i++)            {                AddText(fs, Convert.ToChar(i).ToString());            }        }        //Open the stream and read it back.        using (FileStream fs = File.OpenRead(path))        {            byte[] b = new byte[1024];            UTF8Encoding temp = new UTF8Encoding(true);            int readLen;            while ((readLen = fs.Read(b,0,b.Length)) > 0)            {                Console.WriteLine(temp.GetString(b,0,readLen));            }        }    }    private static void AddText(FileStream fs, string value)    {        byte[] info = new UTF8Encoding(true).GetBytes(value);        fs.Write(info, 0, info.Length);    }}

open Systemopen System.IOopen System.Textlet addText (fs:FileStream) (value: string) =    let info = UTF8Encoding(true).GetBytes value    fs.Write(info, 0, info.Length);let path = @"c:\temp\MyTest.txt"// Delete the file if it exists.if File.Exists path then    File.Delete path//Create the file.do    use fs = File.Create path    addText fs "This is some text"    addText fs "This is some more text,"    addText fs "\r\nand this is on a new line"    addText fs "\r\n\r\nThe following is a subset of characters:\r\n"    for i = 1 to 119 do        Convert.ToChar i        |> string        |> addText fs    do    //Open the stream and read it back.    use fs = File.OpenRead path    let b = Array.zeroCreate 1024    let temp = UTF8Encoding true    let mutable readLen = fs.Read(b,0,b.Length);    while readLen> 0 do        printfn $"{temp.GetString(b,0,readLen)}"        readLen <- fs.Read(b,0,b.Length)

Imports System.IOImports System.TextPublic Class Test    Public Shared Sub Main()        Dim path As String = "c:\temp\MyTest.txt"        ' Delete the file if it exists.        If File.Exists(path) Then            File.Delete(path)        End If        'Create the file.        Dim fs As FileStream = File.Create(path)        AddText(fs, "This is some text")        AddText(fs, "This is some more text,")        AddText(fs, Environment.NewLine & "and this is on a new line")        AddText(fs, Environment.NewLine & Environment.NewLine)        AddText(fs, "The following is a subset of characters:" & Environment.NewLine)        Dim i As Integer        For i = 1 To 120            AddText(fs, Convert.ToChar(i).ToString())        Next        fs.Close()        'Open the stream and read it back.        fs = File.OpenRead(path)        Dim b(1023) As Byte        Dim temp As UTF8Encoding = New UTF8Encoding(True)        Do While fs.Read(b, 0, b.Length) > 0            Console.WriteLine(temp.GetString(b))        Loop        fs.Close()    End Sub    Private Shared Sub AddText(ByVal fs As FileStream, ByVal value As String)        Dim info As Byte() = New UTF8Encoding(True).GetBytes(value)        fs.Write(info, 0, info.Length)    End SubEnd Class

The following example shows how to write to a file asynchronously. This code runs in a WPF app that has a TextBlock named UserInput and a button hooked up to a Click event handler that is named Button_Click. The file path needs to be changed to a file that exists on the computer.

using System;using System.Text;using System.Threading.Tasks;using System.Windows;using System.Windows.Controls;using System.IO;namespace WpfApplication1{    public partial class MainWindow : Window    {        public MainWindow()        {            InitializeComponent();        }        private async void Button_Click(object sender, RoutedEventArgs e)        {            UnicodeEncoding uniencoding = new UnicodeEncoding();            string filename = @"c:\Users\exampleuser\Documents\userinputlog.txt";            byte[] result = uniencoding.GetBytes(UserInput.Text);            using (FileStream SourceStream = File.Open(filename, FileMode.OpenOrCreate))            {                SourceStream.Seek(0, SeekOrigin.End);                await SourceStream.WriteAsync(result, 0, result.Length);            }        }    }}

Imports System.IOImports System.TextClass MainWindow    Private Async Sub Button_Click(sender As Object, e As RoutedEventArgs)        Dim uniencoding As UnicodeEncoding = New UnicodeEncoding()        Dim filename As String = "c:\Users\exampleuser\Documents\userinputlog.txt"        Dim result As Byte() = uniencoding.GetBytes(UserInput.Text)        Using SourceStream As FileStream = File.Open(filename, FileMode.OpenOrCreate)            SourceStream.Seek(0, SeekOrigin.End)            Await SourceStream.WriteAsync(result, 0, result.Length)        End Using    End SubEnd Class

Remarks

For more information about this API, seeSupplemental API remarks for FileStream.

Constructors

Name	Description
FileStream(IntPtr, FileAccess, Boolean, Int32, Boolean)	Obsolete. Obsolete. Obsolete. Initializes a new instance of theFileStream class for the specified file handle, with the specified read/write permission,`FileStream` instance ownership, buffer size, and synchronous or asynchronous state.
FileStream(IntPtr, FileAccess, Boolean, Int32)	Obsolete. Obsolete. Obsolete. Initializes a new instance of theFileStream class for the specified file handle, with the specified read/write permission,`FileStream` instance ownership, and buffer size.
FileStream(IntPtr, FileAccess, Boolean)	Obsolete. Obsolete. Obsolete. Initializes a new instance of theFileStream class for the specified file handle, with the specified read/write permission and`FileStream` instance ownership.
FileStream(IntPtr, FileAccess)	Obsolete. Obsolete. Obsolete. Initializes a new instance of theFileStream class for the specified file handle, with the specified read/write permission.
FileStream(SafeFileHandle, FileAccess, Int32, Boolean)	Initializes a new instance of theFileStream class for the specified file handle, with the specified read/write permission, buffer size, and synchronous or asynchronous state.
FileStream(SafeFileHandle, FileAccess, Int32)	Initializes a new instance of theFileStream class for the specified file handle, with the specified read/write permission, and buffer size.
FileStream(SafeFileHandle, FileAccess)	Initializes a new instance of theFileStream class for the specified file handle, with the specified read/write permission.
FileStream(String, FileMode, FileAccess, FileShare, Int32, Boolean)	Initializes a new instance of theFileStream class with the specified path, creation mode, read/write and sharing permission, buffer size, and synchronous or asynchronous state.
FileStream(String, FileMode, FileAccess, FileShare, Int32, FileOptions)	Initializes a new instance of theFileStream class with the specified path, creation mode, read/write and sharing permission, the access other FileStreams can have to the same file, the buffer size, and additional file options.
FileStream(String, FileMode, FileAccess, FileShare, Int32)	Initializes a new instance of theFileStream class with the specified path, creation mode, read/write and sharing permission, and buffer size.
FileStream(String, FileMode, FileAccess, FileShare)	Initializes a new instance of theFileStream class with the specified path, creation mode, read/write permission, and sharing permission.
FileStream(String, FileMode, FileAccess)	Initializes a new instance of theFileStream class with the specified path, creation mode, and read/write permission.
FileStream(String, FileMode, FileSystemRights, FileShare, Int32, FileOptions, FileSecurity)	Initializes a new instance of theFileStream class with the specified path, creation mode, access rights and sharing permission, the buffer size, additional file options, access control and audit security.
FileStream(String, FileMode, FileSystemRights, FileShare, Int32, FileOptions)	Initializes a new instance of theFileStream class with the specified path, creation mode, access rights and sharing permission, the buffer size, and additional file options.
FileStream(String, FileMode)	Initializes a new instance of theFileStream class with the specified path and creation mode.
FileStream(String, FileStreamOptions)	Initializes a new instance of theFileStream class with the specified path, creation mode, read/write and sharing permission, buffer size, additional file options, preallocation size, and the access other FileStreams can have to the same file.

Properties

Name	Description
CanRead	Gets a value that indicates whether the current stream supports reading.
CanSeek	Gets a value that indicates whether the current stream supports seeking.
CanTimeout	Gets a value that determines whether the current stream can time out. (Inherited fromStream)
CanWrite	Gets a value that indicates whether the current stream supports writing.
Handle	Obsolete. Obsolete. Obsolete. Gets the operating system file handle for the file that the current`FileStream` object encapsulates.
IsAsync	Gets a value that indicates whether the`FileStream` was opened asynchronously or synchronously.
Length	Gets the length in bytes of the stream.
Name	Gets the absolute path of the file opened in the`FileStream`.
Position	Gets or sets the current position of this stream.
ReadTimeout	Gets or sets a value, in milliseconds, that determines how long the stream will attempt to read before timing out. (Inherited fromStream)
SafeFileHandle	Gets aSafeFileHandle object that represents the operating system file handle for the file that the currentFileStream object encapsulates.
WriteTimeout	Gets or sets a value, in milliseconds, that determines how long the stream will attempt to write before timing out. (Inherited fromStream)

Methods

Name	Description
BeginRead(Byte[], Int32, Int32, AsyncCallback, Object)	Begins an asynchronous read operation. Consider usingReadAsync(Byte[], Int32, Int32, CancellationToken) instead.
BeginWrite(Byte[], Int32, Int32, AsyncCallback, Object)	Begins an asynchronous write operation. Consider usingWriteAsync(Byte[], Int32, Int32, CancellationToken) instead.
Close()	Closes the current stream and releases any resources (such as sockets and file handles) associated with the current stream.
Close()	Closes the current stream and releases any resources (such as sockets and file handles) associated with the current stream. Instead of calling this method, ensure that the stream is properly disposed. (Inherited fromStream)
CopyTo(Stream, Int32)	Reads the bytes from the current stream and writes them to another stream, using a specified buffer size. Both streams positions are advanced by the number of bytes copied.
CopyTo(Stream, Int32)	Reads the bytes from the current stream and writes them to another stream, using a specified buffer size. Both streams positions are advanced by the number of bytes copied. (Inherited fromStream)
CopyTo(Stream)	Reads the bytes from the current stream and writes them to another stream. Both streams positions are advanced by the number of bytes copied. (Inherited fromStream)
CopyToAsync(Stream, CancellationToken)	Asynchronously reads the bytes from the current stream and writes them to another stream, using a specified cancellation token. Both streams positions are advanced by the number of bytes copied. (Inherited fromStream)
CopyToAsync(Stream, Int32, CancellationToken)	Asynchronously reads the bytes from the current file stream and writes them to another stream, using a specified buffer size and cancellation token.
CopyToAsync(Stream, Int32, CancellationToken)	Asynchronously reads the bytes from the current stream and writes them to another stream, using a specified buffer size and cancellation token. Both streams positions are advanced by the number of bytes copied. (Inherited fromStream)
CopyToAsync(Stream, Int32)	Asynchronously reads the bytes from the current stream and writes them to another stream, using a specified buffer size. Both streams positions are advanced by the number of bytes copied. (Inherited fromStream)
CopyToAsync(Stream)	Asynchronously reads the bytes from the current stream and writes them to another stream. Both streams positions are advanced by the number of bytes copied. (Inherited fromStream)
CreateObjRef(Type)	Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object. (Inherited fromMarshalByRefObject)
CreateWaitHandle()	Obsolete. Obsolete. Obsolete. Allocates aWaitHandle object. (Inherited fromStream)
Dispose()	Releases all resources used by theStream. (Inherited fromStream)
Dispose(Boolean)	Releases the unmanaged resources used by theFileStream and optionally releases the managed resources.
DisposeAsync()	Asynchronously releases the unmanaged resources used by theFileStream.
EndRead(IAsyncResult)	Waits for the pending asynchronous read operation to complete. (Consider usingReadAsync(Byte[], Int32, Int32, CancellationToken) instead.)
EndWrite(IAsyncResult)	Ends an asynchronous write operation and blocks until the I/O operation is complete. (Consider usingWriteAsync(Byte[], Int32, Int32, CancellationToken) instead.)
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited fromObject)
Finalize()	Ensures that resources are freed and other cleanup operations are performed when the garbage collector reclaims the`FileStream`.
Flush()	Clears buffers for this stream and causes any buffered data to be written to the file.
Flush(Boolean)	Clears buffers for this stream and causes any buffered data to be written to the file, and also clears all intermediate file buffers.
FlushAsync()	Asynchronously clears all buffers for this stream and causes any buffered data to be written to the underlying device. (Inherited fromStream)
FlushAsync(CancellationToken)	Asynchronously clears all buffers for this stream, causes any buffered data to be written to the file, and monitors cancellation requests.
GetAccessControl()	Gets aFileSecurity object that encapsulates the access control list (ACL) entries for the file described by the currentFileStream object.
GetHashCode()	Serves as the default hash function. (Inherited fromObject)
GetLifetimeService()	Obsolete. Retrieves the current lifetime service object that controls the lifetime policy for this instance. (Inherited fromMarshalByRefObject)
GetType()	Gets theType of the current instance. (Inherited fromObject)
InitializeLifetimeService()	Obsolete. Obtains a lifetime service object to control the lifetime policy for this instance. (Inherited fromMarshalByRefObject)
Lock(Int64, Int64)	Prevents other processes from reading from or writing to theFileStream.
MemberwiseClone()	Creates a shallow copy of the currentObject. (Inherited fromObject)
MemberwiseClone(Boolean)	Creates a shallow copy of the currentMarshalByRefObject object. (Inherited fromMarshalByRefObject)
ObjectInvariant()	Obsolete. Provides support for aContract. (Inherited fromStream)
Read(Byte[], Int32, Int32)	Reads a block of bytes from the stream and writes the data in a given buffer.
Read(Span<Byte>)	Reads a sequence of bytes from the current file stream and advances the position within the file stream by the number of bytes read.
Read(Span<Byte>)	When overridden in a derived class, reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read. (Inherited fromStream)
ReadAsync(Byte[], Int32, Int32, CancellationToken)	Asynchronously reads a sequence of bytes from the current file stream and writes them to a byte array beginning at a specified offset, advances the position within the file stream by the number of bytes read, and monitors cancellation requests.
ReadAsync(Byte[], Int32, Int32)	Asynchronously reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read. (Inherited fromStream)
ReadAsync(Memory<Byte>, CancellationToken)	Asynchronously reads a sequence of bytes from the current file stream and writes them to a memory region, advances the position within the file stream by the number of bytes read, and monitors cancellation requests.
ReadAsync(Memory<Byte>, CancellationToken)	Asynchronously reads a sequence of bytes from the current stream, advances the position within the stream by the number of bytes read, and monitors cancellation requests. (Inherited fromStream)
ReadAtLeast(Span<Byte>, Int32, Boolean)	Reads at least a minimum number of bytes from the current stream and advances the position within the stream by the number of bytes read. (Inherited fromStream)
ReadAtLeastAsync(Memory<Byte>, Int32, Boolean, CancellationToken)	Asynchronously reads at least a minimum number of bytes from the current stream, advances the position within the stream by the number of bytes read, and monitors cancellation requests. (Inherited fromStream)
ReadByte()	Reads a byte from the file and advances the read position one byte.
ReadExactly(Byte[], Int32, Int32)	Reads`count` number of bytes from the current stream and advances the position within the stream. (Inherited fromStream)
ReadExactly(Span<Byte>)	Reads bytes from the current stream and advances the position within the stream until the`buffer` is filled. (Inherited fromStream)
ReadExactlyAsync(Byte[], Int32, Int32, CancellationToken)	Asynchronously reads`count` number of bytes from the current stream, advances the position within the stream, and monitors cancellation requests. (Inherited fromStream)
ReadExactlyAsync(Memory<Byte>, CancellationToken)	Asynchronously reads bytes from the current stream, advances the position within the stream until the`buffer` is filled, and monitors cancellation requests. (Inherited fromStream)
Seek(Int64, SeekOrigin)	Sets the current position of this stream to the given value.
SetAccessControl(FileSecurity)	Applies access control list (ACL) entries described by aFileSecurity object to the file described by the currentFileStream object.
SetLength(Int64)	Sets the length of this stream to the given value.
ToString()	Returns a string that represents the current object. (Inherited fromObject)
Unlock(Int64, Int64)	Allows access by other processes to all or part of a file that was previously locked.
Write(Byte[], Int32, Int32)	Writes a block of bytes to the file stream.
Write(ReadOnlySpan<Byte>)	Writes a sequence of bytes from a read-only span to the current file stream and advances the current position within this file stream by the number of bytes written.
Write(ReadOnlySpan<Byte>)	When overridden in a derived class, writes a sequence of bytes to the current stream and advances the current position within this stream by the number of bytes written. (Inherited fromStream)
WriteAsync(Byte[], Int32, Int32, CancellationToken)	Asynchronously writes a sequence of bytes to the current stream, advances the current position within this stream by the number of bytes written, and monitors cancellation requests.
WriteAsync(Byte[], Int32, Int32)	Asynchronously writes a sequence of bytes to the current stream and advances the current position within this stream by the number of bytes written. (Inherited fromStream)
WriteAsync(ReadOnlyMemory<Byte>, CancellationToken)	Asynchronously writes a sequence of bytes from a memory region to the current file stream, advances the current position within this file stream by the number of bytes written, and monitors cancellation requests.
WriteAsync(ReadOnlyMemory<Byte>, CancellationToken)	Asynchronously writes a sequence of bytes to the current stream, advances the current position within this stream by the number of bytes written, and monitors cancellation requests. (Inherited fromStream)
WriteByte(Byte)	Writes a byte to the current position in the file stream.

Explicit Interface Implementations

Name	Description
IDisposable.Dispose()	Releases all resources used by theStream. (Inherited fromStream)

Extension Methods

Name	Description
GetAccessControl(FileStream)	Returns the security information of a file.
SetAccessControl(FileStream, FileSecurity)	Changes the security attributes of an existing file.
CopyToAsync(Stream, PipeWriter, CancellationToken)	Asynchronously reads the bytes from theStream and writes them to the specifiedPipeWriter, using a cancellation token.
AsInputStream(Stream)	Converts a managed stream in the .NET for Windows Store apps to an input stream in the Windows Runtime.
AsOutputStream(Stream)	Converts a managed stream in the .NET for Windows Store apps to an output stream in the Windows Runtime.
AsRandomAccessStream(Stream)	Converts the specified stream to a random access stream.
ConfigureAwait(IAsyncDisposable, Boolean)	Configures how awaits on the tasks returned from an async disposable will be performed.

Applies to

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