MutexAccessRule Class
Assembly: mscorlib (in mscorlib.dll)
The MutexAccessRule class is one of a set of classes that the .NET Framework provides for managing Windows access control security on named system mutexes. For an overview of these classes, and their relationship to the underlying Windows access control structures, see MutexSecurity.
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| Windows access control security is meaningful only for named system mutexes. If a Mutex object represents a local mutex, access control is irrelevant. |
To get a list of the rules currently applied to a named mutex, use the Mutex.GetAccessControl method to get a MutexSecurity object, and then use its GetAccessRules method to obtain a collection of MutexAccessRule objects.
MutexAccessRule 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 mutex, the set contains the minimum number of rules currently required to express all the access control entries.
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| 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 MutexAccessRule objects to specify access rights to allow or deny to a user or group. A MutexAccessRule object always represents either allowed access or denied access, never both.
To apply a rule to a named system mutex, use the Mutex.GetAccessControl method to get the MutexSecurity object. Modify the MutexSecurity object by using its methods to add the rule, and then use the Mutex.SetAccessControl method to reattach the security object.
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| Changes you make to a MutexSecurity object do not affect the access levels of the named mutex until you call the Mutex.SetAccessControl method to assign the altered security object to the named mutex. |
MutexAccessRule objects are immutable. Security for a mutex is modified using the methods of the MutexSecurity class to add or remove rules; as you do this, the underlying access control entries are modified.
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| Security on synchronization objects is not supported for Windows 98 or Windows Millennium Edition. |
The following code example demonstrates the creation and use of MutexAccessRule objects. The example creates a MutexSecurity object, adds rules that allow and deny various rights for the current user, and displays the resulting pair of rules. The example then allows new rights for the current user and displays the result, showing that the new rights are merged with the existing Allow rule.
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| This example does not attach the security object to a Mutex object. Examples that attach security objects can be found in Mutex.GetAccessControl and Mutex.SetAccessControl. |
using System; using System.Threading; using System.Security.AccessControl; using System.Security.Principal; public class Example { public static void Main() { // Create a string representing the current user. string user = Environment.UserDomainName + "\\" + Environment.UserName; // Create a security object that grants no access. MutexSecurity mSec = new MutexSecurity(); // Add a rule that grants the current user the // right to enter or release the mutex. MutexAccessRule rule = new MutexAccessRule(user, MutexRights.Synchronize | MutexRights.Modify, AccessControlType.Allow); mSec.AddAccessRule(rule); // Add a rule that denies the current user the // right to change permissions on the mutex. rule = new MutexAccessRule(user, MutexRights.ChangePermissions, AccessControlType.Deny); mSec.AddAccessRule(rule); // Display the rules in the security object. ShowSecurity(mSec); // Add a rule that allows the current user the // right to read permissions on the mutex. This rule // is merged with the existing Allow rule. rule = new MutexAccessRule(user, MutexRights.ReadPermissions, AccessControlType.Allow); mSec.AddAccessRule(rule); ShowSecurity(mSec); } private static void ShowSecurity(MutexSecurity security) { Console.WriteLine("\r\nCurrent access rules:\r\n"); foreach(MutexAccessRule ar in security.GetAccessRules(true, true, typeof(NTAccount))) { Console.WriteLine(" User: {0}", ar.IdentityReference); Console.WriteLine(" Type: {0}", ar.AccessControlType); Console.WriteLine(" Rights: {0}", ar.MutexRights); Console.WriteLine(); } } } /*This code example produces output similar to following: Current access rules: User: TestDomain\TestUser Type: Deny Rights: ChangePermissions User: TestDomain\TestUser Type: Allow Rights: Modify, Synchronize Current access rules: User: TestDomain\TestUser Type: Deny Rights: ChangePermissions User: TestDomain\TestUser Type: Allow Rights: Modify, ReadPermissions, Synchronize */
System.Security.AccessControl.AuthorizationRule
System.Security.AccessControl.AccessRule
System.Security.AccessControl.MutexAccessRule
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