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FileStream Constructor (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.

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

new : 
        path:string * 
        mode:FileMode * 
        access:FileAccess * 
        share:FileShare * 
        bufferSize:int * 
        useAsync:bool -> FileStream

Parameters

path
Type: System.String
A relative or absolute path for the file that the current FileStream object will encapsulate.
mode
Type: System.IO.FileMode
A constant that determines how to open or create the file.
access
Type: System.IO.FileAccess
A constant that determines how the file can be accessed by the FileStream object. This gets the CanRead and CanWrite properties of the FileStream object. CanSeek is true if path specifies a disk file.
share
Type: System.IO.FileShare
A constant that determines how the file will be shared by processes.
bufferSize
Type: System.Int32
A positive Int32 value greater than 0 indicating the buffer size. For bufferSize values between one and eight, the actual buffer size is set to eight bytes.
useAsync
Type: System.Boolean
Specifies whether to use asynchronous I/O or synchronous I/O. However, note that the underlying operating system might not support asynchronous I/O, so when specifying true, the handle might be opened synchronously depending on the platform. When opened asynchronously, the BeginRead and BeginWrite methods perform better on large reads or writes, but they might be much slower for small reads or writes. If the application is designed to take advantage of asynchronous I/O, set the useAsync parameter to true. Using asynchronous I/O correctly can speed up applications by as much as a factor of 10, but using it without redesigning the application for asynchronous I/O can decrease performance by as much as a factor of 10.

ExceptionCondition
ArgumentNullException

path is a null reference (Nothing in Visual Basic).

ArgumentException

path is an empty string (""), contains only white space, or contains one or more invalid characters.

-or-

path refers to a non-file device, such as "con:", "com1:", "lpt1:", etc. in an NTFS environment.

NotSupportedException

path refers to a non-file device, such as "con:", "com1:", "lpt1:", etc. in a non-NTFS environment.

ArgumentOutOfRangeException

bufferSize is negative or zero.

-or-

mode, access, or share contain an invalid value.

FileNotFoundException

The file cannot be found, such as when mode is FileMode.Truncate or FileMode.Open, and the file specified by path does not exist. The file must already exist in these modes.

IOException

An I/O error, such as specifying FileMode.CreateNew when the file specified by path already exists, occurred.

-or-

The system is running Windows 98 or Windows 98 Second Edition and share is set to FileShare.Delete.

-or-

The stream has been closed.

SecurityException

The caller does not have the required permission.

DirectoryNotFoundException

The specified path is invalid, such as being on an unmapped drive.

UnauthorizedAccessException

The access requested is not permitted by the operating system for the specified path, such as when access is Write or ReadWrite and the file or directory is set for read-only access.

PathTooLongException

The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.

The .NET Framework does not support direct access to physical disks through paths that are device names, such as "\\.\PHYSICALDRIVE0 ".

The path parameter can be a file name, including a file on a Universal Naming Convention (UNC) share.

NoteNote

path is not required to be a file stored on disk; it can be any part of a system that supports access through streams. For example, depending on the system, this class can access a physical device.

CanSeek is true for all FileStream objects that encapsulate files. If path indicates a device that does not support seeking, the CanSeek property on the resulting FileStream is false. For additional information, see CanSeek.

Caution noteCaution

When you compile a set of characters with a particular cultural setting and retrieve those same characters with a different cultural setting, the characters might not be interpretable, and could cause an exception to be thrown.

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

The following code example shows how to asynchronously write data to a file and then verify that the data was written correctly. A State object is created to pass information from the main thread to the EndReadCallback and EndWriteCallback methods.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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