RemoveAccessRuleSpecific Method

EventWaitHandleSecurity.RemoveAccessRuleSpecific Method (EventWaitHandleAccessRule)

 

Searches for an access control rule that exactly matches the specified rule and, if found, removes it.

Namespace:   System.Security.AccessControl
Assembly:  mscorlib (in mscorlib.dll)

public void RemoveAccessRuleSpecific(
	EventWaitHandleAccessRule rule
)

Exception Condition
ArgumentNullException

rule is null.

The rule is removed only if it exactly matches rule in all details, including flags. Other rules with the same user and AccessControlType are not affected.

System_CAPS_importantImportant

A rule represents one or more underlying access control entries (ACE), and these entries are split or combined as necessary when you modify the access security rules for a user. Thus, a rule might no longer exist in the specific form it had when it was added, and in that case the RemoveAccessRuleSpecific method cannot remove it.

The following code example shows that the RemoveAccessRuleSpecific method requires an exact match in order to remove a rule, and that rules to allow and deny rights are independent of each other.

The example creates an EventWaitHandleSecurity object, adds rules that allow and deny various rights for the current user, and then merges additional rights into the Allow access rule. The example then passes the original Allow rule to the RemoveAccessRuleSpecific method, and displays the results, showing that nothing is deleted. The example then constructs a rule that matches the Allow rule in the EventWaitHandleSecurity object, and successfully uses the RemoveAccessRuleSpecific method to remove the rule.

System_CAPS_noteNote

This example does not attach the security object to a EventWaitHandle object. Examples that attach security objects can be found in EventWaitHandle.GetAccessControl and EventWaitHandle.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.
        EventWaitHandleSecurity mSec = new EventWaitHandleSecurity();

        // Add a rule that grants the current user the 
        // right to wait on or signal the event.
        EventWaitHandleAccessRule ruleA = new EventWaitHandleAccessRule(user, 
            EventWaitHandleRights.Synchronize | EventWaitHandleRights.Modify, 
            AccessControlType.Allow);
        mSec.AddAccessRule(ruleA);

        // Add a rule that denies the current user the 
        // right to change permissions on the event.
        EventWaitHandleAccessRule rule = new EventWaitHandleAccessRule(user, 
            EventWaitHandleRights.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 event. This rule
        // is merged with the existing Allow rule.
        rule = new EventWaitHandleAccessRule(user, 
            EventWaitHandleRights.ReadPermissions, 
            AccessControlType.Allow);
        mSec.AddAccessRule(rule);

        ShowSecurity(mSec);

        // Attempt to remove the original rule (granting
        // the right to wait on or signal the event) with 
        // RemoveAccessRuleSpecific. The removal fails,
        // because the right to read the permissions on the 
        // event has been added to the rule, so that it no 
        // longer matches the original rule.
        Console.WriteLine("Attempt to use RemoveAccessRuleSpecific on the original rule.");
        mSec.RemoveAccessRuleSpecific(ruleA);

        ShowSecurity(mSec);

        // Create a rule that grants the current user 
        // the right to wait on or signal the event, and
        // to read permissions. Use this rule to remove
        // the Allow rule for the current user.
        Console.WriteLine("Use RemoveAccessRuleSpecific with the correct rights.");
        rule = new EventWaitHandleAccessRule(user, 
            EventWaitHandleRights.Synchronize | EventWaitHandleRights.Modify | 
                EventWaitHandleRights.ReadPermissions, 
            AccessControlType.Allow);
        mSec.RemoveAccessRuleSpecific(rule);

        ShowSecurity(mSec);
    }

    private static void ShowSecurity(EventWaitHandleSecurity security)
    {
        Console.WriteLine("\r\nCurrent access rules:\r\n");

        foreach(EventWaitHandleAccessRule 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.EventWaitHandleRights);
            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

Attempt to use RemoveAccessRuleSpecific on the original rule.

Current access rules:

        User: TestDomain\TestUser
        Type: Deny
      Rights: ChangePermissions

        User: TestDomain\TestUser
        Type: Allow
      Rights: Modify, ReadPermissions, Synchronize

Use RemoveAccessRuleSpecific with the correct rights.

Current access rules:

        User: TestDomain\TestUser
        Type: Deny
      Rights: ChangePermissions
 */

.NET Framework
Available since 2.0
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