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FileInfo.Open Method (FileMode, FileAccess, FileShare)

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

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

public FileStream Open(
	FileMode mode,
	FileAccess access,
	FileShare share
)

Parameters

mode
Type: System.IO.FileMode

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

access
Type: System.IO.FileAccess

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

share
Type: System.IO.FileShare

A FileShare constant specifying the type of access other FileStream objects have to this file.

Return Value

Type: System.IO.FileStream
A FileStream object opened with the specified mode, access, and sharing options.

ExceptionCondition
SecurityException

The caller does not have the required permission.

FileNotFoundException

The file is not found.

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 example demonstrates opening a file for reading and writing, but disallowing access to other users or processes.

using System;
using System.IO;

public class OpenTest 
{
    public static void Main() 
    {
        // Open an existing file, or create a new one.
        FileInfo fi = new FileInfo("temp.txt");

        // Open the file just specified such that no one else can use it.
        FileStream fs = fi.Open( FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None );

        // Create another reference to the same file.
        FileInfo nextfi = new FileInfo("temp.txt");        

        try 
        {
            // Try opening the same file, which was locked by the previous process.
            nextfi.Open( FileMode.OpenOrCreate, FileAccess.Read );

            Console.WriteLine("The file was not locked, and was opened by a second process.");
        } 
        catch (IOException) 
        {
            Console.WriteLine("The file could not be opened because it was locked by another process.");
        } 
        catch (Exception e) 
        {
            Console.WriteLine(e.ToString());
        }

        // Close the file so it can be deleted.
        fs.Close();
    }
}

//This code produces output similar to the following;  
//results may vary based on the computer/file structure/etc.: 
// 
//The file could not be opened because it was locked by another process.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

.NET for Windows Phone apps

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

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