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FileInfo.Open Method (FileMode, FileAccess)

Opens a file in the specified mode with read, write, or read/write access.

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

public FileStream Open (
	FileMode mode,
	FileAccess access
)
public FileStream Open (
	FileMode mode, 
	FileAccess access
)
public function Open (
	mode : FileMode, 
	access : FileAccess
) : FileStream

Parameters

mode

A FileMode constant specifying the mode (for example, Open or Append) in which to open the file.

access

A FileAccess constant specifying whether to open the file with Read, Write, or ReadWrite file access.

Return Value

A FileStream object opened in the specified mode and access, and unshared.
Exception typeCondition

SecurityException

The caller does not have the required permission.

ArgumentException

path is empty or contains only white spaces.

FileNotFoundException

The file is not found.

ArgumentNullException

One or more arguments is a null reference (Nothing in Visual Basic).

UnauthorizedAccessException

path is read-only or is a directory.

DirectoryNotFoundException

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

IOException

The file is already open.

The following table lists examples of other typical or related I/O tasks.

To do this...

See the example in this topic...

Create a text file.

How to: Write Text to a File

Write to a text file.

How to: Write Text to a File

Read from a text file.

How to: Read Text from a File

Append text to a file.

How to: Open and Append to a Log File

File.AppendText

FileInfo.AppendText

Rename or move a file.

File.Move

FileInfo.MoveTo

Copy a file.

File.Copy

FileInfo.CopyTo

Get the size of a file.

FileInfo.Length

Get the attributes of a file.

File.GetAttributes

Set the attributes of a file.

File.SetAttributes

Determine if a file exists.

File.Exists

Read from a binary file.

How to: Read and Write to a Newly Created Data File

Write to a binary file.

How to: Read and Write to a Newly Created Data File

Create a directory.

CreateDirectory

Directory

The following example opens a file as read-only and reads from the file.

using System;
using System.IO;
using System.Text;

class Test 
{
	
    public static void Main() 
    {
        string path = @"c:\temp\MyTest.txt";
        FileInfo fi = new FileInfo(path);

        // Delete the file if it exists.
        if (!fi.Exists) 
        {
            //Create the file.
            using (FileStream fs = fi.Create()) 
            {
                Byte[] info = new UTF8Encoding(true).GetBytes("This is some text in the file.");
                //Add some information to the file.
                fs.Write(info, 0, info.Length);
            }
        }

        //Open the stream and read it back.
        using (FileStream fs = fi.Open(FileMode.Open, FileAccess.Read)) 
        {
            byte[] b = new byte[1024];
            UTF8Encoding temp = new UTF8Encoding(true);
            while (fs.Read(b,0,b.Length) > 0) 
            {
                Console.WriteLine(temp.GetString(b));
            }

            try 
            {
                //Try to write to the file.
                fs.Write(b,0,b.Length);
            } 
            catch (Exception e) 
            {
                Console.WriteLine("Writing was disallowed, as expected: {0}",
                    e.ToString());
            }
        }
    }
}

import System.*;
import System.IO.*;
import System.Text.*;

class Test
{
    public static void main(String[] args)
    {
        String path = "c:\\temp\\MyTest.txt";
        FileInfo fi = new FileInfo(path);

        // Delete the file if it exists.
        if (!(fi.get_Exists())) {
            //Create the file.
            FileStream fs = fi.Create();

            try {
                ubyte info[] = (new UTF8Encoding(true)).GetBytes("This is " 
                    + "some text in the file.");

                //Add some information to the file.
                fs.Write(info, 0, info.length);
            }
            finally {
                fs.Dispose();
            }
        }

        //Open the stream and read it back.
        FileStream fs = fi.Open(FileMode.Open, FileAccess.Read);

        try {
            ubyte b[] = new ubyte[1024];
            UTF8Encoding temp = new UTF8Encoding(true);

            while ((fs.Read(b, 0, b.length) > 0)) {
                Console.WriteLine(temp.GetString(b));
            }
            try {
                //Try to write to the file.
                fs.Write(b, 0, b.length);
            }
            catch (System.Exception e) {
                Console.WriteLine("Writing was disallowed, as expected: {0}",
                    e.ToString());
            }
        }
      finally {
         fs.Dispose();
      }
    } //main
} //Test

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0
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