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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
Not applicable.

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.

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

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:\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());
            }
        }
    }
}
//This code produces output similar to the following; 
//results may vary based on the computer/file structure/etc.:
//
//This is some text in the file.
//
//
//
//
//
//
//
//
//
//
//
//
//Writing was disallowed, as expected: System.NotSupportedException: Stream does 
//not support writing.
//   at System.IO.__Error.WriteNotSupported()
//   at System.IO.FileStream.Write(Byte[] array, Int32 offset, Int32 count)
//   at Test.Main() in C:\Documents and Settings\My Computer\My Documents\
//Visual Studio 2005\Projects\finfo open2\finfo open2\Program.cs:line 39


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

class Test
{
    public static void main(String[] args)
    {
        String path = "c:\\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
//This code produces output similar to the following; 
//results may vary based on the computer/file structure/etc.:
//
//This is some text in the file.
//
//
//
//
//
//
//
//
//
//
//
//
//Writing was disallowed, as expected: System.NotSupportedException: Stream does 
//not support writing.
//   at System.IO.__Error.WriteNotSupported()
//   at System.IO.FileStream.Write(Byte[] array, Int32 offset, Int32 count)
//   at Test.main(String[] args)
//

Windows 98, Windows Server 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 Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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