File.Open Method (String, FileMode, FileAccess)

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Opens a FileStream on the specified path, with the specified mode and access.

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


Public Shared Function Open ( _
    path As String, _
    mode As FileMode, _
    access As FileAccess _
) As FileStream
public static FileStream Open(
    string path,
    FileMode mode,
    FileAccess access


  • mode
    Type: System.IO..::.FileMode
    A FileMode value that specifies whether a file is created if one does not exist, and determines whether the contents of existing files are retained or overwritten.

Return Value

Type: System.IO..::.FileStream
An unshared FileStream that provides access to the specified file, with the specified mode and access.


Exception Condition

path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by GetInvalidPathChars.


access specified Read and mode specified Create, CreateNew, Truncate, or Append.


path is nullNothingnullptra null reference (Nothing in Visual Basic).


The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.


The specified path is invalid, (for example, it is on an unmapped drive).


An I/O error occurred while opening the file.


path specified a file that is read-only and access is not Read.


path specified a directory.


The caller does not have the required permission.


mode or access specified an invalid value.


The file specified in path was not found.


path is in an invalid format.


Version Notes

Windows Phone

This member has a SecurityCriticalAttribute attribute. This attribute restricts this member to internal use. Application code that uses this member throws a MethodAccessException.

Version Information

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0


Windows Phone

See Also


File Class

Open Overload

System.IO Namespace