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FileMode Enumeration

Specifies how the operating system should open a file.

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

[SerializableAttribute] 
[ComVisibleAttribute(true)] 
public enum FileMode
/** @attribute SerializableAttribute() */ 
/** @attribute ComVisibleAttribute(true) */ 
public enum FileMode
SerializableAttribute 
ComVisibleAttribute(true) 
public enum FileMode

 Member nameDescription
Supported by the .NET Compact FrameworkAppendOpens the file if it exists and seeks to the end of the file, or creates a new file. FileMode.Append can only be used in conjunction with FileAccess.Write. Attempting to seek to a position before the end of the file will throw an IOException and any attempt to read fails and throws an NotSupportedException
Supported by the .NET Compact FrameworkCreateSpecifies that the operating system should create a new file. If the file already exists, it will be overwritten. This requires FileIOPermissionAccess.Write. System.IO.FileMode.Create is equivalent to requesting that if the file does not exist, use CreateNew; otherwise, use Truncate
Supported by the .NET Compact FrameworkCreateNewSpecifies that the operating system should create a new file. This requires FileIOPermissionAccess.Write. If the file already exists, an IOException is thrown. 
Supported by the .NET Compact FrameworkOpenSpecifies that the operating system should open an existing file. The ability to open the file is dependent on the value specified by FileAccess. A System.IO.FileNotFoundException is thrown if the file does not exist. 
Supported by the .NET Compact FrameworkOpenOrCreateSpecifies that the operating system should open a file if it exists; otherwise, a new file should be created. If the file is opened with FileAccess.Read, FileIOPermissionAccess.Read is required. If the file access is FileAccess.Write then FileIOPermissionAccess.Write is required. If the file is opened with FileAccess.ReadWrite, both FileIOPermissionAccess.Read and FileIOPermissionAccess.Write are required. If the file access is FileAccess.Append, then FileIOPermissionAccess.Append is required. 
Supported by the .NET Compact FrameworkTruncateSpecifies that the operating system should open an existing file. Once opened, the file should be truncated so that its size is zero bytes. This requires FileIOPermissionAccess.Write. Attempts to read from a file opened with Truncate cause an exception. 

For an example of creating a file and writing text to a file, see Writing Text to a File. For an example of reading text from a file, see Reading Text from a File. For an example of reading from and writing to a binary file, see Reading and Writing to a Newly Created Data File.

A FileMode parameter is specified in many of the constructors for FileStream, IsolatedStorageFileStream, and in the Open methods of File and FileInfo to control how a file is opened.

FileMode parameters control whether a file is overwritten, created, or opened, or some combination thereof. Use Open to open an existing file. To append to a file, use Append. To truncate a file or to create it if it does not exist, use Create.

Windows Mobile 2003 for Pocket PC, Windows Mobile 2003 for Smartphone, Windows CE Platform Note: Windows CE cannot store more than 999 files in a directory when the files share the same short file name (that is, the eight-character name, period (.), and 3-character extension). The workaround is to ensure that the short file names are different. For example, if the files are named Longfilename0001.txt through Longfilename1000.txt, place the number at the beginning of the file name instead of at the end.

The following FileStream constructor opens an existing file (FileMode.Open).

FileStream s2 = new FileStream(name, FileMode.Open, FileAccess.Read, FileShare.Read);

FileStream s2 = new FileStream(name, FileMode.Open, 
    FileAccess.Read, FileShare.Read);

var s2 : FileStream = new FileStream(name, FileMode.Open, FileAccess.Read, FileShare.Read);

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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