Mutex.OpenExisting Methode

Definition

Öffnet einen bestimmten benannten Mutex, wenn er bereits vorhanden ist.Opens a specified named mutex, if it already exists.

Überlädt

OpenExisting(String)

Öffnet den bestimmten benannten Mutex, wenn er bereits vorhanden ist.Opens the specified named mutex, if it already exists.

OpenExisting(String, MutexRights)

Öffnet den angegebenen benannten Mutex, wenn er bereits vorhanden ist, mit dem gewünschten Sicherheitszugriff.Opens the specified named mutex, if it already exists, with the desired security access.

OpenExisting(String)

Öffnet den bestimmten benannten Mutex, wenn er bereits vorhanden ist.Opens the specified named mutex, if it already exists.

public:
 static System::Threading::Mutex ^ OpenExisting(System::String ^ name);
[System.Security.SecurityCritical]
public static System.Threading.Mutex OpenExisting (string name);
static member OpenExisting : string -> System.Threading.Mutex
Public Shared Function OpenExisting (name As String) As Mutex

Parameter

name
String

Der Name des zu öffnenden Systemmutex.The name of the system mutex to open.

Gibt zurück

Ein Objekt, das den benannten Systemmutex darstellt.An object that represents the named system mutex.

Attribute

Ausnahmen

name ist eine leere Zeichenfolge.name is an empty string.

- oder --or- name ist länger als 260 Zeichen.name is longer than 260 characters.

name ist null.name is null.

Der benannte Mutex ist nicht vorhanden.The named mutex does not exist.

Win32-Fehler.A Win32 error occurred.

Das benannte Mutex ist vorhanden, aber der Benutzer verfügt nicht über den Sicherheitszugriff, der für die Verwendung erforderlich ist.The named mutex exists, but the user does not have the security access required to use it.

Beispiele

Im folgenden Codebeispiel wird das prozessübergreifende Verhalten eines benannten Mutex mit Zugriffs Steuerungs Sicherheit veranschaulicht.The following code example demonstrates the cross-process behavior of a named mutex with access control security. Im Beispiel wird die OpenExisting(String) -Methoden Überladung verwendet, um zu testen, ob ein benannter Mutex vorhanden ist.The example uses the OpenExisting(String) method overload to test for the existence of a named mutex.

Wenn der Mutex nicht vorhanden ist, wird er mit dem anfänglichen Besitz und der Zugriffs Steuerungs Sicherheit erstellt, der dem aktuellen Benutzer das Recht verweigert, den Mutex zu verwenden, gewährt jedoch das Recht, Lese-und Änderungs Berechtigungen für den Mutex zu lesen und zu ändern.If the mutex does not exist, it is created with initial ownership and access control security that denies the current user the right to use the mutex, but grants the right to read and change permissions on the mutex.

Wenn Sie das kompilierte Beispiel aus zwei Befehls Fenstern ausführen, löst die zweite Kopie beim Aufrufen OpenExisting(String)von eine Zugriffs Verletzungs Ausnahme aus.If you run the compiled example from two command windows, the second copy will throw an access violation exception on the call to OpenExisting(String). Die Ausnahme wird abgefangen, und das Beispiel verwendet die OpenExisting(String, MutexRights) -Methoden Überladung, um den Mutex mit den rechten zu öffnen, die zum Lesen und Ändern der Berechtigungen erforderlich sind.The exception is caught, and the example uses the OpenExisting(String, MutexRights) method overload to open the mutex with the rights needed to read and change the permissions.

Nachdem die Berechtigungen geändert wurden, wird der Mutex mit den zum eingeben und Freigeben erforderlichen Rechten geöffnet.After the permissions are changed, the mutex is opened with the rights required to enter and release it. Wenn Sie das kompilierte Beispiel aus einem dritten Befehlsfenster ausführen, wird es mithilfe der neuen Berechtigungen ausgeführt.If you run the compiled example from a third command window, it runs using the new permissions.

using namespace System;
using namespace System::Threading;
using namespace System::Security::AccessControl;
using namespace System::Security::Permissions;

public ref class Example
{
public:
   [SecurityPermissionAttribute(SecurityAction::Demand,Flags=SecurityPermissionFlag::UnmanagedCode)]
   static void Main()
   {
      String^ mutexName = L"MutexExample4";

      Mutex^ m = nullptr;
      bool doesNotExist = false;
      bool unauthorized = false;
      
      // The value of this variable is set by the mutex
      // constructor. It is true if the named system mutex was
      // created, and false if the named mutex already existed.
      //
      bool mutexWasCreated = false;

      // Attempt to open the named mutex.
      try
      {
         // Open the mutex with (MutexRights.Synchronize |
         // MutexRights.Modify), to enter and release the
         // named mutex.
         //
         m = Mutex::OpenExisting( mutexName );
      }
      catch ( WaitHandleCannotBeOpenedException^ ) 
      {
         Console::WriteLine( L"Mutex does not exist." );
         doesNotExist = true;
      }
      catch ( UnauthorizedAccessException^ ex ) 
      {
         Console::WriteLine( L"Unauthorized access: {0}", ex->Message );
         unauthorized = true;
      }

      // There are three cases: (1) The mutex does not exist.
      // (2) The mutex exists, but the current user doesn't
      // have access. (3) The mutex exists and the user has
      // access.
      //
      if ( doesNotExist )
      {
         // The mutex does not exist, so create it.
         // Create an access control list (ACL) that denies the
         // current user the right to enter or release the
         // mutex, but allows the right to read and change
         // security information for the mutex.
         //
         String^ user = String::Concat( Environment::UserDomainName, L"\\",
            Environment::UserName );
         MutexSecurity^ mSec = gcnew MutexSecurity;

         MutexAccessRule^ rule = gcnew MutexAccessRule( user,
            static_cast<MutexRights>(
               MutexRights::Synchronize |
               MutexRights::Modify),
            AccessControlType::Deny );
         mSec->AddAccessRule( rule );

         rule = gcnew MutexAccessRule( user,
            static_cast<MutexRights>(
               MutexRights::ReadPermissions |
                MutexRights::ChangePermissions),
            AccessControlType::Allow );
         mSec->AddAccessRule( rule );
         
         // Create a Mutex object that represents the system
         // mutex named by the constant 'mutexName', with
         // initial ownership for this thread, and with the
         // specified security access. The Boolean value that
         // indicates creation of the underlying system object
         // is placed in mutexWasCreated.
         //
         m = gcnew Mutex( true,mutexName, mutexWasCreated,mSec );
         
         // If the named system mutex was created, it can be
         // used by the current instance of this program, even
         // though the current user is denied access. The current
         // program owns the mutex. Otherwise, exit the program.
         //
         if ( mutexWasCreated )
         {
            Console::WriteLine( L"Created the mutex." );
         }
         else
         {
            Console::WriteLine( L"Unable to create the mutex." );
            return;
         }
      }
      else if ( unauthorized )
      {
         // Open the mutex to read and change the access control
         // security. The access control security defined above
         // allows the current user to do this.
         //
         try
         {
            m = Mutex::OpenExisting( mutexName,
               static_cast<MutexRights>(
                  MutexRights::ReadPermissions |
                  MutexRights::ChangePermissions) );
            
            // Get the current ACL. This requires
            // MutexRights.ReadPermissions.
            MutexSecurity^ mSec = m->GetAccessControl();

            String^ user = String::Concat( Environment::UserDomainName,
               L"\\", Environment::UserName );
            
            // First, the rule that denied the current user
            // the right to enter and release the mutex must
            // be removed.
            MutexAccessRule^ rule = gcnew MutexAccessRule( user,
               static_cast<MutexRights>(
                  MutexRights::Synchronize |
                  MutexRights::Modify),
               AccessControlType::Deny );
            mSec->RemoveAccessRule( rule );
            
            // Now grant the user the correct rights.
            //
            rule = gcnew MutexAccessRule( user,
               static_cast<MutexRights>(
                  MutexRights::Synchronize |
                  MutexRights::Modify),
               AccessControlType::Allow );
            mSec->AddAccessRule( rule );
            
            // Update the ACL. This requires
            // MutexRights.ChangePermissions.
            m->SetAccessControl( mSec );

            Console::WriteLine( L"Updated mutex security." );
            
            // Open the mutex with (MutexRights.Synchronize
            // | MutexRights.Modify), the rights required to
            // enter and release the mutex.
            //
            m = Mutex::OpenExisting( mutexName );
         }
         catch ( UnauthorizedAccessException^ ex ) 
         {
            Console::WriteLine(
               L"Unable to change permissions: {0}", ex->Message );
            return;
         }
      }
      
      // If this program created the mutex, it already owns
      // the mutex.
      //
      if ( !mutexWasCreated )
      {
         // Enter the mutex, and hold it until the program
         // exits.
         //
         try
         {
            Console::WriteLine( L"Wait for the mutex." );
            m->WaitOne();
            Console::WriteLine( L"Entered the mutex." );
         }
         catch ( UnauthorizedAccessException^ ex ) 
         {
            Console::WriteLine( L"Unauthorized access: {0}",
               ex->Message );
         }
      }

      Console::WriteLine( L"Press the Enter key to exit." );
      Console::ReadLine();
      m->ReleaseMutex();
      m->Dispose();
   }
};

int main()
{
   Example::Main();
}
using System;
using System.Threading;
using System.Security.AccessControl;

internal class Example
{
    internal static void Main()
    {
        const string mutexName = "MutexExample4";

        Mutex m = null;
        bool doesNotExist = false;
        bool unauthorized = false;

        // The value of this variable is set by the mutex
        // constructor. It is true if the named system mutex was
        // created, and false if the named mutex already existed.
        //
        bool mutexWasCreated = false;

        // Attempt to open the named mutex.
        try
        {
            // Open the mutex with (MutexRights.Synchronize |
            // MutexRights.Modify), to enter and release the
            // named mutex.
            //
            m = Mutex.OpenExisting(mutexName);
        }
        catch(WaitHandleCannotBeOpenedException)
        {
            Console.WriteLine("Mutex does not exist.");
            doesNotExist = true;
        }
        catch(UnauthorizedAccessException ex)
        {
            Console.WriteLine("Unauthorized access: {0}", ex.Message);
            unauthorized = true;
        }

        // There are three cases: (1) The mutex does not exist.
        // (2) The mutex exists, but the current user doesn't 
        // have access. (3) The mutex exists and the user has
        // access.
        //
        if (doesNotExist)
        {
            // The mutex does not exist, so create it.

            // Create an access control list (ACL) that denies the
            // current user the right to enter or release the 
            // mutex, but allows the right to read and change
            // security information for the mutex.
            //
            string user = Environment.UserDomainName + "\\"
                + Environment.UserName;
            MutexSecurity mSec = new MutexSecurity();

            MutexAccessRule rule = new MutexAccessRule(user, 
                MutexRights.Synchronize | MutexRights.Modify, 
                AccessControlType.Deny);
            mSec.AddAccessRule(rule);

            rule = new MutexAccessRule(user, 
                MutexRights.ReadPermissions | MutexRights.ChangePermissions,
                AccessControlType.Allow);
            mSec.AddAccessRule(rule);

            // Create a Mutex object that represents the system
            // mutex named by the constant 'mutexName', with
            // initial ownership for this thread, and with the
            // specified security access. The Boolean value that 
            // indicates creation of the underlying system object
            // is placed in mutexWasCreated.
            //
            m = new Mutex(true, mutexName, out mutexWasCreated, mSec);

            // If the named system mutex was created, it can be
            // used by the current instance of this program, even 
            // though the current user is denied access. The current
            // program owns the mutex. Otherwise, exit the program.
            // 
            if (mutexWasCreated)
            {
                Console.WriteLine("Created the mutex.");
            }
            else
            {
                Console.WriteLine("Unable to create the mutex.");
                return;
            }

        }
        else if (unauthorized)
        {
            // Open the mutex to read and change the access control
            // security. The access control security defined above
            // allows the current user to do this.
            //
            try
            {
                m = Mutex.OpenExisting(mutexName, 
                    MutexRights.ReadPermissions | MutexRights.ChangePermissions);

                // Get the current ACL. This requires 
                // MutexRights.ReadPermissions.
                MutexSecurity mSec = m.GetAccessControl();
                
                string user = Environment.UserDomainName + "\\"
                    + Environment.UserName;

                // First, the rule that denied the current user 
                // the right to enter and release the mutex must
                // be removed.
                MutexAccessRule rule = new MutexAccessRule(user, 
                     MutexRights.Synchronize | MutexRights.Modify,
                     AccessControlType.Deny);
                mSec.RemoveAccessRule(rule);

                // Now grant the user the correct rights.
                // 
                rule = new MutexAccessRule(user, 
                    MutexRights.Synchronize | MutexRights.Modify,
                    AccessControlType.Allow);
                mSec.AddAccessRule(rule);

                // Update the ACL. This requires
                // MutexRights.ChangePermissions.
                m.SetAccessControl(mSec);

                Console.WriteLine("Updated mutex security.");

                // Open the mutex with (MutexRights.Synchronize 
                // | MutexRights.Modify), the rights required to
                // enter and release the mutex.
                //
                m = Mutex.OpenExisting(mutexName);

            }
            catch(UnauthorizedAccessException ex)
            {
                Console.WriteLine("Unable to change permissions: {0}",
                    ex.Message);
                return;
            }

        }

        // If this program created the mutex, it already owns
        // the mutex.
        //
        if (!mutexWasCreated)
        {
            // Enter the mutex, and hold it until the program
            // exits.
            //
            try
            {
                Console.WriteLine("Wait for the mutex.");
                m.WaitOne();
                Console.WriteLine("Entered the mutex.");
            }
            catch(UnauthorizedAccessException ex)
            {
                Console.WriteLine("Unauthorized access: {0}", ex.Message);
            }
        }

        Console.WriteLine("Press the Enter key to exit.");
        Console.ReadLine();
        m.ReleaseMutex();
        m.Dispose();
    }
}
Imports System.Threading
Imports System.Security.AccessControl

Friend Class Example

    <MTAThread> _
    Friend Shared Sub Main()
        Const mutexName As String = "MutexExample4"

        Dim m As Mutex = Nothing
        Dim doesNotExist as Boolean = False
        Dim unauthorized As Boolean = False

        ' The value of this variable is set by the mutex
        ' constructor. It is True if the named system mutex was
        ' created, and False if the named mutex already existed.
        '
        Dim mutexWasCreated As Boolean

        ' Attempt to open the named mutex.
        Try
            ' Open the mutex with (MutexRights.Synchronize Or
            ' MutexRights.Modify), to enter and release the
            ' named mutex.
            '
            m = Mutex.OpenExisting(mutexName)
        Catch ex As WaitHandleCannotBeOpenedException
            Console.WriteLine("Mutex does not exist.")
            doesNotExist = True
        Catch ex As UnauthorizedAccessException
            Console.WriteLine("Unauthorized access: {0}", ex.Message)
            unauthorized = True
        End Try

        ' There are three cases: (1) The mutex does not exist.
        ' (2) The mutex exists, but the current user doesn't 
        ' have access. (3) The mutex exists and the user has
        ' access.
        '
        If doesNotExist Then
            ' The mutex does not exist, so create it.

            ' Create an access control list (ACL) that denies the
            ' current user the right to enter or release the 
            ' mutex, but allows the right to read and change
            ' security information for the mutex.
            '
            Dim user As String = Environment.UserDomainName _ 
                & "\" & Environment.UserName
            Dim mSec As New MutexSecurity()

            Dim rule As New MutexAccessRule(user, _
                MutexRights.Synchronize Or MutexRights.Modify, _
                AccessControlType.Deny)
            mSec.AddAccessRule(rule)

            rule = New MutexAccessRule(user, _
                MutexRights.ReadPermissions Or _
                MutexRights.ChangePermissions, _
                AccessControlType.Allow)
            mSec.AddAccessRule(rule)

            ' Create a Mutex object that represents the system
            ' mutex named by the constant 'mutexName', with
            ' initial ownership for this thread, and with the
            ' specified security access. The Boolean value that 
            ' indicates creation of the underlying system object
            ' is placed in mutexWasCreated.
            '
            m = New Mutex(True, mutexName, mutexWasCreated, mSec)

            ' If the named system mutex was created, it can be
            ' used by the current instance of this program, even 
            ' though the current user is denied access. The current
            ' program owns the mutex. Otherwise, exit the program.
            ' 
            If mutexWasCreated Then
                Console.WriteLine("Created the mutex.")
            Else
                Console.WriteLine("Unable to create the mutex.")
                Return
            End If

        ElseIf unauthorized Then

            ' Open the mutex to read and change the access control
            ' security. The access control security defined above
            ' allows the current user to do this.
            '
            Try
                m = Mutex.OpenExisting(mutexName, _
                    MutexRights.ReadPermissions Or _
                    MutexRights.ChangePermissions)

                ' Get the current ACL. This requires 
                ' MutexRights.ReadPermissions.
                Dim mSec As MutexSecurity = m.GetAccessControl()
                
                Dim user As String = Environment.UserDomainName _ 
                    & "\" & Environment.UserName

                ' First, the rule that denied the current user 
                ' the right to enter and release the mutex must
                ' be removed.
                Dim rule As New MutexAccessRule(user, _
                    MutexRights.Synchronize Or MutexRights.Modify, _
                    AccessControlType.Deny)
                mSec.RemoveAccessRule(rule)

                ' Now grant the user the correct rights.
                ' 
                rule = New MutexAccessRule(user, _
                    MutexRights.Synchronize Or MutexRights.Modify, _
                    AccessControlType.Allow)
                mSec.AddAccessRule(rule)

                ' Update the ACL. This requires
                ' MutexRights.ChangePermissions.
                m.SetAccessControl(mSec)

                Console.WriteLine("Updated mutex security.")

                ' Open the mutex with (MutexRights.Synchronize 
                ' Or MutexRights.Modify), the rights required to
                ' enter and release the mutex.
                '
                m = Mutex.OpenExisting(mutexName)

            Catch ex As UnauthorizedAccessException
                Console.WriteLine("Unable to change permissions: {0}", _
                    ex.Message)
                Return
            End Try

        End If

        ' If this program created the mutex, it already owns
        ' the mutex.
        '
        If Not mutexWasCreated Then
            ' Enter the mutex, and hold it until the program
            ' exits.
            '
            Try
                Console.WriteLine("Wait for the mutex.")
                m.WaitOne()
                Console.WriteLine("Entered the mutex.")
            Catch ex As UnauthorizedAccessException
                Console.WriteLine("Unauthorized access: {0}", _
                    ex.Message)
            End Try
        End If

        Console.WriteLine("Press the Enter key to exit.")
        Console.ReadLine()
        m.ReleaseMutex()
        m.Dispose()
    End Sub 
End Class 

Hinweise

Die OpenExisting -Methode versucht, den angegebenen benannten Systemmutex zu öffnen.The OpenExisting method tries to open the specified named system mutex. Wenn der Systemmutex nicht vorhanden ist, löst diese Methode eine Ausnahme aus, statt das Systemobjekt zu erstellen.If the system mutex does not exist, this method throws an exception instead of creating the system object. Um den Systemmutex zu erstellen, wenn er nicht bereits vorhanden ist, verwenden Sie Mutex einen der-Konstruktoren name mit einem-Parameter.To create the system mutex when it does not already exist, use one of the Mutex constructors that has a name parameter.

Mehrere Aufrufe dieser Methode, die denselben Wert für name verwenden, geben nicht notwendigerweise dasselbe Mutex Objekt zurück, auch wenn die zurückgegebenen Objekte denselben benannten Systemmutex darstellen.Multiple calls to this method that use the same value for name do not necessarily return the same Mutex object, even though the objects that are returned represent the same named system mutex.

Diese Methoden Überladung entspricht dem Aufrufen der OpenExisting(String, MutexRights) -Methoden Überladung MutexRights.Synchronize und MutexRights.Modify der Angabe von-und-rechten in Kombination mit der bitweisen OR-Operation.This method overload is equivalent to calling the OpenExisting(String, MutexRights) method overload and specifying MutexRights.Synchronize and MutexRights.Modify rights, combined by using the bitwise OR operation.

Wenn Sie MutexRights.Synchronize das Flag angeben, kann ein Thread auf den Mutex warten, und MutexRights.Modify die Angabe des Flags ermöglicht einem Thread ReleaseMutex , die Methode aufzurufen.Specifying the MutexRights.Synchronize flag allows a thread to wait on the mutex, and specifying the MutexRights.Modify flag allows a thread to call the ReleaseMutex method.

Diese Methode fordert den Besitz des Mutex nicht an.This method does not request ownership of the mutex.

Sicherheit

SecurityCriticalAttribute
Erfordert volle Vertrauenswürdigkeit für den unmittelbaren Aufrufer.Requires full trust for the immediate caller. Dieser Member kann nicht von teilweise vertrauenswürdigem oder transparentem Code verwendet werden.This member cannot be used by partially trusted or transparent code.

OpenExisting(String, MutexRights)

Öffnet den angegebenen benannten Mutex, wenn er bereits vorhanden ist, mit dem gewünschten Sicherheitszugriff.Opens the specified named mutex, if it already exists, with the desired security access.

public:
 static System::Threading::Mutex ^ OpenExisting(System::String ^ name, System::Security::AccessControl::MutexRights rights);
[System.Security.SecurityCritical]
public static System.Threading.Mutex OpenExisting (string name, System.Security.AccessControl.MutexRights rights);
static member OpenExisting : string * System.Security.AccessControl.MutexRights -> System.Threading.Mutex
Public Shared Function OpenExisting (name As String, rights As MutexRights) As Mutex

Parameter

name
String

Der Name des zu öffnenden Systemmutex.The name of the system mutex to open.

rights
MutexRights

Eine bitweise Kombination von Enumerationswerten, die die gewünschten Sicherheitszugriffsrechte darstellen.A bitwise combination of the enumeration values that represent the desired security access.

Gibt zurück

Ein Objekt, das den benannten Systemmutex darstellt.An object that represents the named system mutex.

Attribute

Ausnahmen

name ist eine leere Zeichenfolge.name is an empty string.

- oder --or- name ist länger als 260 Zeichen.name is longer than 260 characters.

name ist null.name is null.

Der benannte Mutex ist nicht vorhanden.The named mutex does not exist.

Win32-Fehler.A Win32 error occurred.

Der benannte Mutex ist vorhanden aber der Benutzer verfügt nicht über den gewünschten Sicherheitszugriff.The named mutex exists, but the user does not have the desired security access.

Beispiele

Im folgenden Codebeispiel wird das prozessübergreifende Verhalten eines benannten Mutex mit Zugriffs Steuerungs Sicherheit veranschaulicht.The following code example demonstrates the cross-process behavior of a named mutex with access control security. Im Beispiel wird die OpenExisting(String) -Methoden Überladung verwendet, um zu testen, ob ein benannter Mutex vorhanden ist.The example uses the OpenExisting(String) method overload to test for the existence of a named mutex.

Wenn der Mutex nicht vorhanden ist, wird er mit dem anfänglichen Besitz und der Zugriffs Steuerungs Sicherheit erstellt, der dem aktuellen Benutzer das Recht verweigert, den Mutex zu verwenden, gewährt jedoch das Recht, Lese-und Änderungs Berechtigungen für den Mutex zu lesen und zu ändern.If the mutex does not exist, it is created with initial ownership and access control security that denies the current user the right to use the mutex, but grants the right to read and change permissions on the mutex.

Wenn Sie das kompilierte Beispiel aus zwei Befehls Fenstern ausführen, löst die zweite Kopie beim Aufrufen OpenExisting(String)von eine Zugriffs Verletzungs Ausnahme aus.If you run the compiled example from two command windows, the second copy will throw an access violation exception on the call to OpenExisting(String). Die Ausnahme wird abgefangen, und das Beispiel verwendet die OpenExisting(String, MutexRights) -Methoden Überladung, um den Mutex mit den rechten zu öffnen, die zum Lesen und Ändern der Berechtigungen erforderlich sind.The exception is caught, and the example uses the OpenExisting(String, MutexRights) method overload to open the mutex with the rights needed to read and change the permissions.

Nachdem die Berechtigungen geändert wurden, wird der Mutex mit den zum eingeben und Freigeben erforderlichen Rechten geöffnet.After the permissions are changed, the mutex is opened with the rights required to enter and release it. Wenn Sie das kompilierte Beispiel aus einem dritten Befehlsfenster ausführen, wird es mithilfe der neuen Berechtigungen ausgeführt.If you run the compiled example from a third command window, it runs using the new permissions.

using namespace System;
using namespace System::Threading;
using namespace System::Security::AccessControl;
using namespace System::Security::Permissions;

public ref class Example
{
public:
   [SecurityPermissionAttribute(SecurityAction::Demand,Flags=SecurityPermissionFlag::UnmanagedCode)]
   static void Main()
   {
      String^ mutexName = L"MutexExample4";

      Mutex^ m = nullptr;
      bool doesNotExist = false;
      bool unauthorized = false;
      
      // The value of this variable is set by the mutex
      // constructor. It is true if the named system mutex was
      // created, and false if the named mutex already existed.
      //
      bool mutexWasCreated = false;

      // Attempt to open the named mutex.
      try
      {
         // Open the mutex with (MutexRights.Synchronize |
         // MutexRights.Modify), to enter and release the
         // named mutex.
         //
         m = Mutex::OpenExisting( mutexName );
      }
      catch ( WaitHandleCannotBeOpenedException^ ) 
      {
         Console::WriteLine( L"Mutex does not exist." );
         doesNotExist = true;
      }
      catch ( UnauthorizedAccessException^ ex ) 
      {
         Console::WriteLine( L"Unauthorized access: {0}", ex->Message );
         unauthorized = true;
      }

      // There are three cases: (1) The mutex does not exist.
      // (2) The mutex exists, but the current user doesn't
      // have access. (3) The mutex exists and the user has
      // access.
      //
      if ( doesNotExist )
      {
         // The mutex does not exist, so create it.
         // Create an access control list (ACL) that denies the
         // current user the right to enter or release the
         // mutex, but allows the right to read and change
         // security information for the mutex.
         //
         String^ user = String::Concat( Environment::UserDomainName, L"\\",
            Environment::UserName );
         MutexSecurity^ mSec = gcnew MutexSecurity;

         MutexAccessRule^ rule = gcnew MutexAccessRule( user,
            static_cast<MutexRights>(
               MutexRights::Synchronize |
               MutexRights::Modify),
            AccessControlType::Deny );
         mSec->AddAccessRule( rule );

         rule = gcnew MutexAccessRule( user,
            static_cast<MutexRights>(
               MutexRights::ReadPermissions |
                MutexRights::ChangePermissions),
            AccessControlType::Allow );
         mSec->AddAccessRule( rule );
         
         // Create a Mutex object that represents the system
         // mutex named by the constant 'mutexName', with
         // initial ownership for this thread, and with the
         // specified security access. The Boolean value that
         // indicates creation of the underlying system object
         // is placed in mutexWasCreated.
         //
         m = gcnew Mutex( true,mutexName, mutexWasCreated,mSec );
         
         // If the named system mutex was created, it can be
         // used by the current instance of this program, even
         // though the current user is denied access. The current
         // program owns the mutex. Otherwise, exit the program.
         //
         if ( mutexWasCreated )
         {
            Console::WriteLine( L"Created the mutex." );
         }
         else
         {
            Console::WriteLine( L"Unable to create the mutex." );
            return;
         }
      }
      else if ( unauthorized )
      {
         // Open the mutex to read and change the access control
         // security. The access control security defined above
         // allows the current user to do this.
         //
         try
         {
            m = Mutex::OpenExisting( mutexName,
               static_cast<MutexRights>(
                  MutexRights::ReadPermissions |
                  MutexRights::ChangePermissions) );
            
            // Get the current ACL. This requires
            // MutexRights.ReadPermissions.
            MutexSecurity^ mSec = m->GetAccessControl();

            String^ user = String::Concat( Environment::UserDomainName,
               L"\\", Environment::UserName );
            
            // First, the rule that denied the current user
            // the right to enter and release the mutex must
            // be removed.
            MutexAccessRule^ rule = gcnew MutexAccessRule( user,
               static_cast<MutexRights>(
                  MutexRights::Synchronize |
                  MutexRights::Modify),
               AccessControlType::Deny );
            mSec->RemoveAccessRule( rule );
            
            // Now grant the user the correct rights.
            //
            rule = gcnew MutexAccessRule( user,
               static_cast<MutexRights>(
                  MutexRights::Synchronize |
                  MutexRights::Modify),
               AccessControlType::Allow );
            mSec->AddAccessRule( rule );
            
            // Update the ACL. This requires
            // MutexRights.ChangePermissions.
            m->SetAccessControl( mSec );

            Console::WriteLine( L"Updated mutex security." );
            
            // Open the mutex with (MutexRights.Synchronize
            // | MutexRights.Modify), the rights required to
            // enter and release the mutex.
            //
            m = Mutex::OpenExisting( mutexName );
         }
         catch ( UnauthorizedAccessException^ ex ) 
         {
            Console::WriteLine(
               L"Unable to change permissions: {0}", ex->Message );
            return;
         }
      }
      
      // If this program created the mutex, it already owns
      // the mutex.
      //
      if ( !mutexWasCreated )
      {
         // Enter the mutex, and hold it until the program
         // exits.
         //
         try
         {
            Console::WriteLine( L"Wait for the mutex." );
            m->WaitOne();
            Console::WriteLine( L"Entered the mutex." );
         }
         catch ( UnauthorizedAccessException^ ex ) 
         {
            Console::WriteLine( L"Unauthorized access: {0}",
               ex->Message );
         }
      }

      Console::WriteLine( L"Press the Enter key to exit." );
      Console::ReadLine();
      m->ReleaseMutex();
      m->Dispose();
   }
};

int main()
{
   Example::Main();
}
using System;
using System.Threading;
using System.Security.AccessControl;

internal class Example
{
    internal static void Main()
    {
        const string mutexName = "MutexExample4";

        Mutex m = null;
        bool doesNotExist = false;
        bool unauthorized = false;

        // The value of this variable is set by the mutex
        // constructor. It is true if the named system mutex was
        // created, and false if the named mutex already existed.
        //
        bool mutexWasCreated = false;

        // Attempt to open the named mutex.
        try
        {
            // Open the mutex with (MutexRights.Synchronize |
            // MutexRights.Modify), to enter and release the
            // named mutex.
            //
            m = Mutex.OpenExisting(mutexName);
        }
        catch(WaitHandleCannotBeOpenedException)
        {
            Console.WriteLine("Mutex does not exist.");
            doesNotExist = true;
        }
        catch(UnauthorizedAccessException ex)
        {
            Console.WriteLine("Unauthorized access: {0}", ex.Message);
            unauthorized = true;
        }

        // There are three cases: (1) The mutex does not exist.
        // (2) The mutex exists, but the current user doesn't 
        // have access. (3) The mutex exists and the user has
        // access.
        //
        if (doesNotExist)
        {
            // The mutex does not exist, so create it.

            // Create an access control list (ACL) that denies the
            // current user the right to enter or release the 
            // mutex, but allows the right to read and change
            // security information for the mutex.
            //
            string user = Environment.UserDomainName + "\\"
                + Environment.UserName;
            MutexSecurity mSec = new MutexSecurity();

            MutexAccessRule rule = new MutexAccessRule(user, 
                MutexRights.Synchronize | MutexRights.Modify, 
                AccessControlType.Deny);
            mSec.AddAccessRule(rule);

            rule = new MutexAccessRule(user, 
                MutexRights.ReadPermissions | MutexRights.ChangePermissions,
                AccessControlType.Allow);
            mSec.AddAccessRule(rule);

            // Create a Mutex object that represents the system
            // mutex named by the constant 'mutexName', with
            // initial ownership for this thread, and with the
            // specified security access. The Boolean value that 
            // indicates creation of the underlying system object
            // is placed in mutexWasCreated.
            //
            m = new Mutex(true, mutexName, out mutexWasCreated, mSec);

            // If the named system mutex was created, it can be
            // used by the current instance of this program, even 
            // though the current user is denied access. The current
            // program owns the mutex. Otherwise, exit the program.
            // 
            if (mutexWasCreated)
            {
                Console.WriteLine("Created the mutex.");
            }
            else
            {
                Console.WriteLine("Unable to create the mutex.");
                return;
            }

        }
        else if (unauthorized)
        {
            // Open the mutex to read and change the access control
            // security. The access control security defined above
            // allows the current user to do this.
            //
            try
            {
                m = Mutex.OpenExisting(mutexName, 
                    MutexRights.ReadPermissions | MutexRights.ChangePermissions);

                // Get the current ACL. This requires 
                // MutexRights.ReadPermissions.
                MutexSecurity mSec = m.GetAccessControl();
                
                string user = Environment.UserDomainName + "\\"
                    + Environment.UserName;

                // First, the rule that denied the current user 
                // the right to enter and release the mutex must
                // be removed.
                MutexAccessRule rule = new MutexAccessRule(user, 
                     MutexRights.Synchronize | MutexRights.Modify,
                     AccessControlType.Deny);
                mSec.RemoveAccessRule(rule);

                // Now grant the user the correct rights.
                // 
                rule = new MutexAccessRule(user, 
                    MutexRights.Synchronize | MutexRights.Modify,
                    AccessControlType.Allow);
                mSec.AddAccessRule(rule);

                // Update the ACL. This requires
                // MutexRights.ChangePermissions.
                m.SetAccessControl(mSec);

                Console.WriteLine("Updated mutex security.");

                // Open the mutex with (MutexRights.Synchronize 
                // | MutexRights.Modify), the rights required to
                // enter and release the mutex.
                //
                m = Mutex.OpenExisting(mutexName);

            }
            catch(UnauthorizedAccessException ex)
            {
                Console.WriteLine("Unable to change permissions: {0}",
                    ex.Message);
                return;
            }

        }

        // If this program created the mutex, it already owns
        // the mutex.
        //
        if (!mutexWasCreated)
        {
            // Enter the mutex, and hold it until the program
            // exits.
            //
            try
            {
                Console.WriteLine("Wait for the mutex.");
                m.WaitOne();
                Console.WriteLine("Entered the mutex.");
            }
            catch(UnauthorizedAccessException ex)
            {
                Console.WriteLine("Unauthorized access: {0}", ex.Message);
            }
        }

        Console.WriteLine("Press the Enter key to exit.");
        Console.ReadLine();
        m.ReleaseMutex();
        m.Dispose();
    }
}
Imports System.Threading
Imports System.Security.AccessControl

Friend Class Example

    <MTAThread> _
    Friend Shared Sub Main()
        Const mutexName As String = "MutexExample4"

        Dim m As Mutex = Nothing
        Dim doesNotExist as Boolean = False
        Dim unauthorized As Boolean = False

        ' The value of this variable is set by the mutex
        ' constructor. It is True if the named system mutex was
        ' created, and False if the named mutex already existed.
        '
        Dim mutexWasCreated As Boolean

        ' Attempt to open the named mutex.
        Try
            ' Open the mutex with (MutexRights.Synchronize Or
            ' MutexRights.Modify), to enter and release the
            ' named mutex.
            '
            m = Mutex.OpenExisting(mutexName)
        Catch ex As WaitHandleCannotBeOpenedException
            Console.WriteLine("Mutex does not exist.")
            doesNotExist = True
        Catch ex As UnauthorizedAccessException
            Console.WriteLine("Unauthorized access: {0}", ex.Message)
            unauthorized = True
        End Try

        ' There are three cases: (1) The mutex does not exist.
        ' (2) The mutex exists, but the current user doesn't 
        ' have access. (3) The mutex exists and the user has
        ' access.
        '
        If doesNotExist Then
            ' The mutex does not exist, so create it.

            ' Create an access control list (ACL) that denies the
            ' current user the right to enter or release the 
            ' mutex, but allows the right to read and change
            ' security information for the mutex.
            '
            Dim user As String = Environment.UserDomainName _ 
                & "\" & Environment.UserName
            Dim mSec As New MutexSecurity()

            Dim rule As New MutexAccessRule(user, _
                MutexRights.Synchronize Or MutexRights.Modify, _
                AccessControlType.Deny)
            mSec.AddAccessRule(rule)

            rule = New MutexAccessRule(user, _
                MutexRights.ReadPermissions Or _
                MutexRights.ChangePermissions, _
                AccessControlType.Allow)
            mSec.AddAccessRule(rule)

            ' Create a Mutex object that represents the system
            ' mutex named by the constant 'mutexName', with
            ' initial ownership for this thread, and with the
            ' specified security access. The Boolean value that 
            ' indicates creation of the underlying system object
            ' is placed in mutexWasCreated.
            '
            m = New Mutex(True, mutexName, mutexWasCreated, mSec)

            ' If the named system mutex was created, it can be
            ' used by the current instance of this program, even 
            ' though the current user is denied access. The current
            ' program owns the mutex. Otherwise, exit the program.
            ' 
            If mutexWasCreated Then
                Console.WriteLine("Created the mutex.")
            Else
                Console.WriteLine("Unable to create the mutex.")
                Return
            End If

        ElseIf unauthorized Then

            ' Open the mutex to read and change the access control
            ' security. The access control security defined above
            ' allows the current user to do this.
            '
            Try
                m = Mutex.OpenExisting(mutexName, _
                    MutexRights.ReadPermissions Or _
                    MutexRights.ChangePermissions)

                ' Get the current ACL. This requires 
                ' MutexRights.ReadPermissions.
                Dim mSec As MutexSecurity = m.GetAccessControl()
                
                Dim user As String = Environment.UserDomainName _ 
                    & "\" & Environment.UserName

                ' First, the rule that denied the current user 
                ' the right to enter and release the mutex must
                ' be removed.
                Dim rule As New MutexAccessRule(user, _
                    MutexRights.Synchronize Or MutexRights.Modify, _
                    AccessControlType.Deny)
                mSec.RemoveAccessRule(rule)

                ' Now grant the user the correct rights.
                ' 
                rule = New MutexAccessRule(user, _
                    MutexRights.Synchronize Or MutexRights.Modify, _
                    AccessControlType.Allow)
                mSec.AddAccessRule(rule)

                ' Update the ACL. This requires
                ' MutexRights.ChangePermissions.
                m.SetAccessControl(mSec)

                Console.WriteLine("Updated mutex security.")

                ' Open the mutex with (MutexRights.Synchronize 
                ' Or MutexRights.Modify), the rights required to
                ' enter and release the mutex.
                '
                m = Mutex.OpenExisting(mutexName)

            Catch ex As UnauthorizedAccessException
                Console.WriteLine("Unable to change permissions: {0}", _
                    ex.Message)
                Return
            End Try

        End If

        ' If this program created the mutex, it already owns
        ' the mutex.
        '
        If Not mutexWasCreated Then
            ' Enter the mutex, and hold it until the program
            ' exits.
            '
            Try
                Console.WriteLine("Wait for the mutex.")
                m.WaitOne()
                Console.WriteLine("Entered the mutex.")
            Catch ex As UnauthorizedAccessException
                Console.WriteLine("Unauthorized access: {0}", _
                    ex.Message)
            End Try
        End If

        Console.WriteLine("Press the Enter key to exit.")
        Console.ReadLine()
        m.ReleaseMutex()
        m.Dispose()
    End Sub 
End Class 

Hinweise

Der rights -Parameter muss das MutexRights.Synchronize -Flag enthalten, damit Threads auf den Mutex warten können, MutexRights.Modify und das-Flag, mit dem ReleaseMutex Threads die-Methode aufrufen können.The rights parameter must include the MutexRights.Synchronize flag to allow threads to wait on the mutex, and the MutexRights.Modify flag to allow threads to call the ReleaseMutex method.

Die OpenExisting -Methode versucht, einen vorhandenen benannten Mutex zu öffnen.The OpenExisting method tries to open an existing named mutex. Wenn der Systemmutex nicht vorhanden ist, löst diese Methode eine Ausnahme aus, statt das Systemobjekt zu erstellen.If the system mutex does not exist, this method throws an exception instead of creating the system object. Um den Systemmutex zu erstellen, wenn er nicht bereits vorhanden ist, verwenden Sie Mutex einen der-Konstruktoren name mit einem-Parameter.To create the system mutex when it does not already exist, use one of the Mutex constructors that has a name parameter.

Mehrere Aufrufe dieser Methode, die denselben Wert für name verwenden, geben nicht notwendigerweise dasselbe Mutex Objekt zurück, auch wenn die zurückgegebenen Objekte denselben benannten Systemmutex darstellen.Multiple calls to this method that use the same value for name do not necessarily return the same Mutex object, even though the objects that are returned represent the same named system mutex.

Diese Methode fordert den Besitz des Mutex nicht an.This method does not request ownership of the mutex.

Sicherheit

SecurityCriticalAttribute
Erfordert volle Vertrauenswürdigkeit für den unmittelbaren Aufrufer.Requires full trust for the immediate caller. Dieser Member kann nicht von teilweise vertrauenswürdigem oder transparentem Code verwendet werden.This member cannot be used by partially trusted or transparent code.

Gilt für: