Specifies how the operating system should open a file.
Assembly: mscorlib (in mscorlib.dll)
|Specifies that the operating system should create a new file. This operation requires FileIOPermissionAccess::Write permission. If the file already exists, an IOException exception is thrown.|
|Specifies that the operating system should create a new file. If the file already exists, it will be overwritten. This operation requires FileIOPermissionAccess::Write permission. System.IO.FileMode.Create is equivalent to requesting that if the file does not exist, use ; otherwise, use . If the file already exists but is a hidden file, an UnauthorizedAccessException exception is thrown.|
|Specifies that the operating system should open an existing file. The ability to open the file is dependent on the value specified by the FileAccess enumeration. A System.IO::FileNotFoundException exception is thrown if the file does not exist.|
|Specifies 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 permission is required. If the file access is FileAccess.Write, FileIOPermissionAccess::Write permission is required. If the file is opened with FileAccess.ReadWrite, both FileIOPermissionAccess::Read and FileIOPermissionAccess::Write permissions are required.|
|Specifies that the operating system should open an existing file. When the file is opened, it should be truncated so that its size is zero bytes. This operation requires FileIOPermissionAccess::Write permission. Attempts to read from a file opened with FileMode.Truncate cause an exception.|
|Opens the file if it exists and seeks to the end of the file, or creates a new file. This operation requires FileIOPermissionAccess::Append permission. FileMode.Append can be used only in conjunction with FileAccess.Write. Trying to seek to a position before the end of the file throws an IOException exception, and any attempt to read fails and throws an NotSupportedException exception.|
For an example of creating a file and writing text to a file, see How to: Write Text to a File. For an example of reading text from a file, see How to: Read Text from a File. For an example of reading from and writing to a binary file, see How to: Read and Write to a Newly Created Data File.
FileMode parameters control whether a file is overwritten, created, opened, or some combination thereof. Use Open to open an existing file. To append to a file, use Append. To truncate a file or create a file if it doesn't exist, use Create.
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.