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FileStream Constructor (String, FileMode)

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

Namespace:  System.IO
Assembly:  mscorlib (in mscorlib.dll)
public FileStream(
	string path,
	FileMode mode
)

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.

ExceptionCondition
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.

ArgumentNullException

path is null.

SecurityException

The caller does not have the required permission.

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 stream has been closed.

DirectoryNotFoundException

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

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.

ArgumentOutOfRangeException

mode contains an invalid value.

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.

The constructor is given read/write access to the file, and it is opened sharing Read access (that is, requests to open the file for writing by this or another process will fail until the FileStream object has been closed, but read attempts will succeed). The buffer size is set to the default size of 4096 bytes (4 KB).

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.

FileShare.Read is the default for those FileStream constructors without a FileShare parameter.

For constructors without a FileAccess parameter, if the mode parameter is set to Append, Write is the default access. Otherwise, the access is set to ReadWrite.

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 file and directory operations, see Common I/O Tasks.

The following code example shows how to write data to a file, byte by byte, and then verify that the data was written correctly.

using System;
using System.IO;

class FStream
{
    static void Main()
    {
        const string fileName = "Test#@@#.dat";

        // Create random data to write to the file. 
        byte[] dataArray = new byte[100000];
        new Random().NextBytes(dataArray);

        using(FileStream  
            fileStream = new FileStream(fileName, FileMode.Create))
        {
            // Write the data to the file, byte by byte. 
            for(int i = 0; i < dataArray.Length; i++)
            {
                fileStream.WriteByte(dataArray[i]);
            }

            // Set the stream position to the beginning of the file.
            fileStream.Seek(0, SeekOrigin.Begin);

            // Read and verify the data. 
            for(int i = 0; i < fileStream.Length; i++)
            {
                if(dataArray[i] != fileStream.ReadByte())
                {
                    Console.WriteLine("Error writing data.");
                    return;
                }
            }
            Console.WriteLine("The data was written to {0} " +
                "and verified.", fileStream.Name);
        }
    }
}

.NET Framework

Supported in: 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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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