LockCookie Struct

Definizione

Spazio dei nomi:

System.Threading

Assembly:

netstandard.dll, System.Threading.dll

Origine:

LockCookie.cs

Definisce il blocco che implementa la semantica single-writer/multiple-reader. Si tratta di un tipo valore.

public value class LockCookie : IEquatable<System::Threading::LockCookie>

public struct LockCookie : IEquatable<System.Threading.LockCookie>

type LockCookie = struct

Public Structure LockCookie
Implements IEquatable(Of LockCookie)

Ereditarietà

Object

ValueType

LockCookie

Implementazioni

IEquatable<LockCookie>

Esempio

Nell'esempio seguente viene illustrato come richiedere un blocco lettore, aggiornare il blocco lettore a un blocco writer e salvare .LockCookie Viene quindi usato per effettuare di nuovo il LockCookie downgrade a un blocco lettore.

Questo codice fa parte di un esempio più ampio fornito per la ReaderWriterLock classe .

// The complete code is located in the ReaderWriterLock class topic.
using System;
using System.Threading;

public class Example
{
   static ReaderWriterLock rwl = new ReaderWriterLock();
   // Define the shared resource protected by the ReaderWriterLock.
   static int resource = 0;

' The complete code is located in the ReaderWriterLock class topic.
Imports System.Threading

Public Module Example
   Private rwl As New ReaderWriterLock()
   ' Define the shared resource protected by the ReaderWriterLock.
   Private resource As Integer = 0

// Requests a reader lock, upgrades the reader lock to the writer
// lock, and downgrades it to a reader lock again.
static void UpgradeDowngrade(Random rnd, int timeOut)
{
   try {
      rwl.AcquireReaderLock(timeOut);
      try {
         // It's safe for this thread to read from the shared resource.
         Display("reads resource value " + resource);
         Interlocked.Increment(ref reads);

         // To write to the resource, either release the reader lock and
         // request the writer lock, or upgrade the reader lock. Upgrading
         // the reader lock puts the thread in the write queue, behind any
         // other threads that might be waiting for the writer lock.
         try {
            LockCookie lc = rwl.UpgradeToWriterLock(timeOut);
            try {
               // It's safe for this thread to read or write from the shared resource.
               resource = rnd.Next(500);
               Display("writes resource value " + resource);
               Interlocked.Increment(ref writes);
            }
            finally {
               // Ensure that the lock is released.
               rwl.DowngradeFromWriterLock(ref lc);
            }
         }
         catch (ApplicationException) {
            // The upgrade request timed out.
            Interlocked.Increment(ref writerTimeouts);
         }

         // If the lock was downgraded, it's still safe to read from the resource.
         Display("reads resource value " + resource);
         Interlocked.Increment(ref reads);
      }
      finally {
         // Ensure that the lock is released.
         rwl.ReleaseReaderLock();
      }
   }
   catch (ApplicationException) {
      // The reader lock request timed out.
      Interlocked.Increment(ref readerTimeouts);
   }
}

' Requests a reader lock, upgrades the reader lock to the writer
' lock, and downgrades it to a reader lock again.
Sub UpgradeDowngrade(rnd As Random, timeOut As Integer)
   Try
      rwl.AcquireReaderLock(timeOut)
      Try
         ' It's safe for this thread to read from the shared resource.
         Display("reads resource value " & resource)
         Interlocked.Increment(reads)
         
         ' To write to the resource, either release the reader lock and
         ' request the writer lock, or upgrade the reader lock. Upgrading
         ' the reader lock puts the thread in the write queue, behind any
         ' other threads that might be waiting for the writer lock.
         Try
            Dim lc As LockCookie = rwl.UpgradeToWriterLock(timeOut)
            Try
               ' It's safe for this thread to read or write from the shared resource.
               resource = rnd.Next(500)
               Display("writes resource value " & resource)
               Interlocked.Increment(writes)
            Finally
               ' Ensure that the lock is released.
               rwl.DowngradeFromWriterLock(lc)
            End Try
         Catch ex As ApplicationException
            ' The upgrade request timed out.
            Interlocked.Increment(writerTimeouts)
         End Try
         
         ' If the lock was downgraded, it's still safe to read from the resource.
         Display("reads resource value " & resource)
         Interlocked.Increment(reads)
      Finally
         ' Ensure that the lock is released.
         rwl.ReleaseReaderLock()
      End Try
   Catch ex As ApplicationException
      ' The reader lock request timed out.
      Interlocked.Increment(readerTimeouts)
   End Try
End Sub

}

End Module

Metodi

Nome	Descrizione
Equals(LockCookie)	Indica se l'istanza corrente è uguale all'oggetto specificato LockCookie.
Equals(Object)	Indica se un oggetto specificato è un LockCookie oggetto e è uguale all'istanza corrente.
GetHashCode()	Restituisce il codice hash per questa istanza.

Operatori

Nome	Descrizione
Equality(LockCookie, LockCookie)	Indica se due LockCookie strutture sono uguali.
Inequality(LockCookie, LockCookie)	Indica se due LockCookie strutture non sono uguali.

Thread safety

Questo tipo è thread-safe.

Vedi anche

• ReaderWriterLock
• di threading gestito
• blocchiReader-Writer