System.Security.AccessControl.SemaphoreAccessRule Class

Represents a set of access rights allowed or denied for a user or group. This class cannot be inherited.

See Also: SemaphoreAccessRule Members


public sealed class SemaphoreAccessRule : AccessRule


The System.Security.AccessControl.SemaphoreAccessRule class is one of a set of classes that the .NET Framework provides for managing Windows access control security on named system semaphores. For an overview of these classes, and their relationship to the underlying Windows access control structures, see System.Security.AccessControl.SemaphoreSecurity.


Windows access control security is meaningful only for named system semaphores. If a System.Threading.Semaphore object represents a local semaphore, access control is irrelevant.

To get a list of the rules currently applied to a named semaphore, use the System.Threading.Semaphore.GetAccessControl method to get a System.Security.AccessControl.SemaphoreSecurity object, then use its CommonObjectSecurity.GetAccessRules(bool, bool, Type) method to obtain a collection of System.Security.AccessControl.SemaphoreAccessRule objects.

System.Security.AccessControl.SemaphoreAccessRule objects do not map one-to-one with access control entries in the underlying discretionary access control list (DACL). When you get the set of all access rules for a semaphore, the set contains the minimum number of rules currently required to express all the access control entries.


The underlying access control entries change as you apply and remove rules. The information in rules is merged if possible, to maintain the smallest number of access control entries. Thus, when you read the current list of rules, it might not look exactly like the list of all the rules you have added.

Use System.Security.AccessControl.SemaphoreAccessRule objects to specify access rights to allow or deny to a user or group. A System.Security.AccessControl.SemaphoreAccessRule object always represents either allowed access or denied access, never both.

To apply a rule to a named system semaphore, use the System.Threading.Semaphore.GetAccessControl method to get the System.Security.AccessControl.SemaphoreSecurity object. Modify the System.Security.AccessControl.SemaphoreSecurity object by using its methods to add the rule, and then use the System.Threading.Semaphore.SetAccessControl(SemaphoreSecurity) method to reattach the security object.


Changes you make to a System.Security.AccessControl.SemaphoreSecurity object do not affect the access levels of the named semaphore until you call the System.Threading.Semaphore.SetAccessControl(SemaphoreSecurity) method to assign the altered security object to the named semaphore.

System.Security.AccessControl.SemaphoreAccessRule objects are immutable. Security for a semaphore is modified using the methods of the System.Security.AccessControl.SemaphoreSecurity class to add or remove rules; as you do this, the underlying access control entries are modified.


Security on synchronization objects is not supported for Windows 98 or Windows Millennium Edition.


Namespace: System.Security.AccessControl
Assembly: System (in System.dll)
Assembly Versions:,
Since: .NET 2.0