FileStream Class

FileStream Class

 

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

To browse the .NET Framework source code for this type, see the Reference Source.

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


[ComVisibleAttribute(true)]
public class FileStream : Stream

NameDescription
System_CAPS_pubmethodFileStream(IntPtr, FileAccess)

Obsolete.Initializes a new instance of the FileStream class for the specified file handle, with the specified read/write permission.

System_CAPS_pubmethodFileStream(IntPtr, FileAccess, Boolean)

Obsolete.Initializes a new instance of the FileStream class for the specified file handle, with the specified read/write permission and FileStream instance ownership.

System_CAPS_pubmethodFileStream(IntPtr, FileAccess, Boolean, Int32)

Obsolete.Initializes a new instance of the FileStream class for the specified file handle, with the specified read/write permission, FileStream instance ownership, and buffer size.

System_CAPS_pubmethodFileStream(IntPtr, FileAccess, Boolean, Int32, Boolean)

Obsolete.Initializes a new instance of the FileStream class for the specified file handle, with the specified read/write permission, FileStream instance ownership, buffer size, and synchronous or asynchronous state.

System_CAPS_pubmethodFileStream(SafeFileHandle, FileAccess)

Initializes a new instance of the FileStream class for the specified file handle, with the specified read/write permission.

System_CAPS_pubmethodFileStream(SafeFileHandle, FileAccess, Int32)

Initializes a new instance of the FileStream class for the specified file handle, with the specified read/write permission, and buffer size.

System_CAPS_pubmethodFileStream(SafeFileHandle, FileAccess, Int32, Boolean)

Initializes a new instance of the FileStream class for the specified file handle, with the specified read/write permission, buffer size, and synchronous or asynchronous state.

System_CAPS_pubmethodFileStream(String, FileMode)

Initializes a new instance of the FileStream class with the specified path and creation mode.

System_CAPS_pubmethodFileStream(String, FileMode, FileAccess)

Initializes a new instance of the FileStream class with the specified path, creation mode, and read/write permission.

System_CAPS_pubmethodFileStream(String, FileMode, FileAccess, FileShare)

Initializes a new instance of the FileStream class with the specified path, creation mode, read/write permission, and sharing permission.

System_CAPS_pubmethodFileStream(String, FileMode, FileAccess, FileShare, Int32)

Initializes a new instance of the FileStream class with the specified path, creation mode, read/write and sharing permission, and buffer size.

System_CAPS_pubmethodFileStream(String, FileMode, FileAccess, FileShare, Int32, Boolean)

Initializes a new instance of the FileStream class with the specified path, creation mode, read/write and sharing permission, buffer size, and synchronous or asynchronous state.

System_CAPS_pubmethodFileStream(String, FileMode, FileAccess, FileShare, Int32, FileOptions)

Initializes a new instance of the FileStream 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.

System_CAPS_pubmethodFileStream(String, FileMode, FileSystemRights, FileShare, Int32, FileOptions)

Initializes a new instance of the FileStream class with the specified path, creation mode, access rights and sharing permission, the buffer size, and additional file options.

System_CAPS_pubmethodFileStream(String, FileMode, FileSystemRights, FileShare, Int32, FileOptions, FileSecurity)

Initializes a new instance of the FileStream class with the specified path, creation mode, access rights and sharing permission, the buffer size, additional file options, access control and audit security.

NameDescription
System_CAPS_pubpropertyCanRead

Gets a value indicating whether the current stream supports reading.(Overrides Stream.CanRead.)

System_CAPS_pubpropertyCanSeek

Gets a value indicating whether the current stream supports seeking.(Overrides Stream.CanSeek.)

System_CAPS_pubpropertyCanTimeout

Gets a value that determines whether the current stream can time out.(Inherited from Stream.)

System_CAPS_pubpropertyCanWrite

Gets a value indicating whether the current stream supports writing.(Overrides Stream.CanWrite.)

System_CAPS_pubpropertyHandle

Obsolete.Gets the operating system file handle for the file that the current FileStream object encapsulates.

System_CAPS_pubpropertyIsAsync

Gets a value indicating whether the FileStream was opened asynchronously or synchronously.

System_CAPS_pubpropertyLength

Gets the length in bytes of the stream.(Overrides Stream.Length.)

System_CAPS_pubpropertyName

Gets the name of the FileStream that was passed to the constructor.

System_CAPS_pubpropertyPosition

Gets or sets the current position of this stream.(Overrides Stream.Position.)

System_CAPS_pubpropertyReadTimeout

Gets or sets a value, in miliseconds, that determines how long the stream will attempt to read before timing out. (Inherited from Stream.)

System_CAPS_pubpropertySafeFileHandle

Gets a SafeFileHandle object that represents the operating system file handle for the file that the current FileStream object encapsulates.

System_CAPS_pubpropertyWriteTimeout

Gets or sets a value, in miliseconds, that determines how long the stream will attempt to write before timing out. (Inherited from Stream.)

NameDescription
System_CAPS_pubmethodBeginRead(Byte[], Int32, Int32, AsyncCallback, Object)

Begins an asynchronous read operation. (Consider using ReadAsync instead; see the Remarks section.)(Overrides Stream.BeginRead(Byte[], Int32, Int32, AsyncCallback, Object).)

System_CAPS_pubmethodBeginWrite(Byte[], Int32, Int32, AsyncCallback, Object)

Begins an asynchronous write operation. (Consider using WriteAsync instead; see the Remarks section.)(Overrides Stream.BeginWrite(Byte[], Int32, Int32, AsyncCallback, Object).)

System_CAPS_pubmethodClose()

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 from Stream.)

System_CAPS_pubmethodCopyTo(Stream)

Reads the bytes from the current stream and writes them to another stream.(Inherited from Stream.)

System_CAPS_pubmethodCopyTo(Stream, Int32)

Reads the bytes from the current stream and writes them to another stream, using a specified buffer size.(Inherited from Stream.)

System_CAPS_pubmethodCopyToAsync(Stream)

Asynchronously reads the bytes from the current stream and writes them to another stream.(Inherited from Stream.)

System_CAPS_pubmethodCopyToAsync(Stream, Int32)

Asynchronously reads the bytes from the current stream and writes them to another stream, using a specified buffer size.(Inherited from Stream.)

System_CAPS_pubmethodCopyToAsync(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.(Inherited from Stream.)

System_CAPS_pubmethodCreateObjRef(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.)

System_CAPS_protmethodCreateWaitHandle()

Obsolete.Allocates a WaitHandle object.(Inherited from Stream.)

System_CAPS_pubmethodDispose()

Releases all resources used by the Stream.(Inherited from Stream.)

System_CAPS_protmethodDispose(Boolean)

Releases the unmanaged resources used by the FileStream and optionally releases the managed resources.(Overrides Stream.Dispose(Boolean).)

System_CAPS_pubmethodEndRead(IAsyncResult)

Waits for the pending asynchronous read operation to complete. (Consider using ReadAsync instead; see the Remarks section.)(Overrides Stream.EndRead(IAsyncResult).)

System_CAPS_pubmethodEndWrite(IAsyncResult)

Ends an asynchronous write operation and blocks until the I/O operation is complete. (Consider using WriteAsync instead; see the Remarks section.)(Overrides Stream.EndWrite(IAsyncResult).)

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Ensures that resources are freed and other cleanup operations are performed when the garbage collector reclaims the FileStream.(Overrides Object.Finalize().)

System_CAPS_pubmethodFlush()

Clears buffers for this stream and causes any buffered data to be written to the file.(Overrides Stream.Flush().)

System_CAPS_pubmethodFlush(Boolean)

Clears buffers for this stream and causes any buffered data to be written to the file, and also clears all intermediate file buffers.

System_CAPS_pubmethodFlushAsync()

Asynchronously clears all buffers for this stream and causes any buffered data to be written to the underlying device.(Inherited from Stream.)

System_CAPS_pubmethodFlushAsync(CancellationToken)

Asynchronously clears all buffers for this stream, causes any buffered data to be written to the underlying device, and monitors cancellation requests. (Overrides Stream.FlushAsync(CancellationToken).)

System_CAPS_pubmethodGetAccessControl()

Gets a FileSecurity object that encapsulates the access control list (ACL) entries for the file described by the current FileStream object.

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetLifetimeService()

Retrieves the current lifetime service object that controls the lifetime policy for this instance.(Inherited from MarshalByRefObject.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethodInitializeLifetimeService()

Obtains a lifetime service object to control the lifetime policy for this instance.(Inherited from MarshalByRefObject.)

System_CAPS_pubmethodLock(Int64, Int64)

Prevents other processes from reading from or writing to the FileStream.

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_protmethodMemberwiseClone(Boolean)

Creates a shallow copy of the current MarshalByRefObject object.(Inherited from MarshalByRefObject.)

System_CAPS_protmethodObjectInvariant()

Obsolete. This API supports the product infrastructure and is not intended to be used directly from your code. Provides support for a Contract.(Inherited from Stream.)

System_CAPS_pubmethodRead(Byte[], Int32, Int32)

Reads a block of bytes from the stream and writes the data in a given buffer.(Overrides Stream.Read(Byte[], Int32, Int32).)

System_CAPS_pubmethodReadAsync(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 from Stream.)

System_CAPS_pubmethodReadAsync(Byte[], Int32, Int32, 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.(Overrides Stream.ReadAsync(Byte[], Int32, Int32, CancellationToken).)

System_CAPS_pubmethodReadByte()

Reads a byte from the file and advances the read position one byte.(Overrides Stream.ReadByte().)

System_CAPS_pubmethodSeek(Int64, SeekOrigin)

Sets the current position of this stream to the given value.(Overrides Stream.Seek(Int64, SeekOrigin).)

System_CAPS_pubmethodSetAccessControl(FileSecurity)

Applies access control list (ACL) entries described by a FileSecurity object to the file described by the current FileStream object.

System_CAPS_pubmethodSetLength(Int64)

Sets the length of this stream to the given value.(Overrides Stream.SetLength(Int64).)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

System_CAPS_pubmethodUnlock(Int64, Int64)

Allows access by other processes to all or part of a file that was previously locked.

System_CAPS_pubmethodWrite(Byte[], Int32, Int32)

Writes a block of bytes to the file stream.(Overrides Stream.Write(Byte[], Int32, Int32).)

System_CAPS_pubmethodWriteAsync(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 from Stream.)

System_CAPS_pubmethodWriteAsync(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. (Overrides Stream.WriteAsync(Byte[], Int32, Int32, CancellationToken).)

System_CAPS_pubmethodWriteByte(Byte)

Writes a byte to the current position in the file stream.(Overrides Stream.WriteByte(Byte).)

System_CAPS_noteNote

To view the .NET Framework source code for this type, see the Reference Source. You can browse through the source code online, download the reference for offline viewing, and step through the sources (including patches and updates) during debugging; see instructions.

Use the FileStream class to read from, write to, open, and close files on a file system, and to manipulate other file-related operating system handles, including pipes, standard input, and standard output. You can use the Read, Write, CopyTo, and Flush methods to perform synchronous operations, or the ReadAsync, WriteAsync, CopyToAsync, and FlushAsync methods to perform asynchronous operations. Use the asynchronous methods to perform resource-intensive file operations without blocking the main thread. This performance consideration is particularly important in a Windows 8.x Store app or desktop app where a time-consuming stream operation can block the UI thread and make your app appear as if it is not working. FileStream buffers input and output for better performance.

System_CAPS_importantImportant

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.

The IsAsync property detects whether the file handle was opened asynchronously. You specify this value when you create an instance of the FileStream class using a constructor that has an isAsync, useAsync, or options parameter. When the property is true, the stream utilizes overlapped I/O to perform file operations asynchronously. However, the IsAsync property does not have to be true to call the ReadAsync, WriteAsync, or CopyToAsync method. When the IsAsync property is false and you call the asynchronous read and write operations, the UI thread is still not blocked, but the actual I/O operation is performed synchronously.

The Seek method supports random access to files. Seek allows the read/write position to be moved to any position within the file. This is done with byte offset reference point parameters. The byte offset is relative to the seek reference point, which can be the beginning, the current position, or the end of the underlying file, as represented by the three members of the SeekOrigin enumeration.

System_CAPS_noteNote

Disk files always support random access. At the time of construction, the CanSeek property value is set to true or false depending on the underlying file type.If the underlying file type is FILE_TYPE_DISK, as defined in winbase.h, the CanSeek property value is true. Otherwise, the CanSeek property value is false.

If a process terminates with part of a file locked or closes a file that has outstanding locks, the behavior is undefined.

For directory operations and other file operations, see the File, Directory, and Path classes. The File class is a utility class that has static methods primarily for the creation of FileStream objects based on file paths. The MemoryStream class creates a stream from a byte array and is similar to the FileStream class.

For a list of common file and directory operations, see Common I/O Tasks.

When a FileStream object does not have an exclusive hold on its handle, another thread could access the file handle concurrently and change the position of the operating system's file pointer that is associated with the file handle. In this case, the cached position in the FileStream object and the cached data in the buffer could be compromised. The FileStream object routinely performs checks on methods that access the cached buffer to ensure that the operating system's handle position is the same as the cached position used by the FileStream object.

If an unexpected change in the handle position is detected in a call to the Read method, the .NET Framework discards the contents of the buffer and reads the stream from the file again. This can affect performance, depending on the size of the file and any other processes that could affect the position of the file stream.

If an unexpected change in the handle position is detected in a call to the Write method, the contents of the buffer are discarded and an IOException exception is thrown.

A FileStream object will not have an exclusive hold on its handle when either the SafeFileHandle property is accessed to expose the handle or the FileStream object is given the SafeFileHandle property in its constructor.

The following example demonstrates some of the FileStream 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);
            while (fs.Read(b,0,b.Length) > 0)
            {
                Console.WriteLine(temp.GetString(b));
            }
        }
    }

    private static void AddText(FileStream fs, string value)
    {
        byte[] info = new UTF8Encoding(true).GetBytes(value);
        fs.Write(info, 0, info.Length);
    }
}

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 than exits 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);
            }
        }
    }
}

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0

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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