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FileIOPermissionAttribute Class

Allows security actions for FileIOPermission to be applied to code using declarative security. This class cannot be inherited.

For a list of all members of this type, see FileIOPermissionAttribute Members.


[Visual Basic]
<AttributeUsage(AttributeTargets.Assembly Or AttributeTargets.Class _
   Or AttributeTargets.Struct Or AttributeTargets.Constructor Or _
NotInheritable Public Class FileIOPermissionAttribute
   Inherits CodeAccessSecurityAttribute
[AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class
   | AttributeTargets.Struct | AttributeTargets.Constructor |
public sealed class FileIOPermissionAttribute :
[AttributeUsage(AttributeTargets::Assembly |
   AttributeTargets::Class | AttributeTargets::Struct |
   AttributeTargets::Constructor | AttributeTargets::Method)]
public __gc __sealed class FileIOPermissionAttribute : public
   AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class |
   AttributeTargets.Struct | AttributeTargets.Constructor |
class FileIOPermissionAttribute extends

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.


Files and directories are specified using absolute paths. When accessing files, a security check is performed when the file is created or opened. The security check is not done again unless the file is closed and reopened. Checking permissions when the file is first accessed minimizes the impact of the security check on application performance because opening a file happens only once, while reading and writing can happen multiple times.

The scope of the declaration that is allowed depends on the SecurityAction that is used.

The security information declared by a security attribute is stored in the metadata of the attribute target and is accessed by the system at run time. Security attributes are used only for declarative security. For imperative security, use the corresponding permission class.

CAUTION    Unrestricted FileIOPermission grants permission for all paths within a file system, including multiple pathnames that can be used to access a single given file. To Deny access to a file, you must Deny all possible paths to the file. For example, if \\server\share is mapped to the network drive X, to Deny access to \\server\share\file, you must Deny\\server\share\file, X:\file and any other path that you can use to access the file.


[Visual Basic, C#, C++] The following example of a declarative attribute shows the correct way to request FileIOPermission for full access to the specified file and states that you must have at least this permission to run your code.

[Visual Basic] 
<Assembly: FileIOPermissionAttribute(SecurityAction.RequestMinimum, _
All := "C:\example\sample.txt")>
'In Visual Basic, you must specify that you are using the assembly scope when making a request.

[assembly:FileIOPermissionAttribute(SecurityAction.RequestMinimum, All="C:\\example\\sample.txt")]
//In C#, you must specify that you are using the assembly scope when making a request.

[assembly:FileIOPermissionAttribute(SecurityAction::RequestMinimum, All=S"C:\\example\\sample.txt")];
//In C++, you must specify that you are using the assembly scope when making a request.

[Visual Basic, C#, C++] The following example shows how to demand that the calling code has unrestricted FileIOPermission at link time. You typically make demands in managed libraries (DLLs) to help protect methods or classes from potentially harmful code.

[Visual Basic] 
<FileIOPermissionAttribute(SecurityAction.Demand, _
 Unrestricted := True)> Public Class SampleClass

[FileIOPermissionAttribute(SecurityAction.Demand, Unrestricted=true)]

[FileIOPermissionAttribute(SecurityAction::Demand, Unrestricted=true)]

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.


Namespace: System.Security.Permissions

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

Assembly: Mscorlib (in Mscorlib.dll)

See Also

FileIOPermissionAttribute Members | System.Security.Permissions Namespace | Extending Metadata Using Attributes | FileIOPermission | FileIOPermissionAccess

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