Interlocked.CompareExchange Metodo

Origine:

Interlocked.cs

Origine:

Interlocked.cs

Origine:

Interlocked.cs

public:
 static UIntPtr CompareExchange(UIntPtr % location1, UIntPtr value, UIntPtr comparand);

[System.CLSCompliant(false)]
public static UIntPtr CompareExchange (ref UIntPtr location1, UIntPtr value, UIntPtr comparand);

[<System.CLSCompliant(false)>]
static member CompareExchange : unativeint * unativeint * unativeint -> unativeint

Public Shared Function CompareExchange (ByRef location1 As UIntPtr, value As UIntPtr, comparand As UIntPtr) As UIntPtr

Parametri

Restituisce

Valore originale in location1.

Attributi

CLSCompliantAttribute

Eccezioni

Origine:

Interlocked.cs

Origine:

Interlocked.cs

Origine:

Interlocked.cs

public:
 static System::UInt64 CompareExchange(System::UInt64 % location1, System::UInt64 value, System::UInt64 comparand);

[System.CLSCompliant(false)]
public static ulong CompareExchange (ref ulong location1, ulong value, ulong comparand);

[<System.CLSCompliant(false)>]
static member CompareExchange : uint64 * uint64 * uint64 -> uint64

Public Shared Function CompareExchange (ByRef location1 As ULong, value As ULong, comparand As ULong) As ULong

Parametri

Restituisce

Valore originale in location1.

Attributi

CLSCompliantAttribute

Eccezioni

Origine:

Interlocked.cs

Origine:

Interlocked.cs

Origine:

Interlocked.cs

public:
 static System::UInt32 CompareExchange(System::UInt32 % location1, System::UInt32 value, System::UInt32 comparand);

[System.CLSCompliant(false)]
public static uint CompareExchange (ref uint location1, uint value, uint comparand);

[<System.CLSCompliant(false)>]
static member CompareExchange : uint32 * uint32 * uint32 -> uint32

Public Shared Function CompareExchange (ByRef location1 As UInteger, value As UInteger, comparand As UInteger) As UInteger

Parametri

Restituisce

Valore originale in location1.

Attributi

CLSCompliantAttribute

Eccezioni

public:
 static System::UInt16 CompareExchange(System::UInt16 % location1, System::UInt16 value, System::UInt16 comparand);

[System.CLSCompliant(false)]
public static ushort CompareExchange (ref ushort location1, ushort value, ushort comparand);

[<System.CLSCompliant(false)>]
static member CompareExchange : uint16 * uint16 * uint16 -> uint16

Public Shared Function CompareExchange (ByRef location1 As UShort, value As UShort, comparand As UShort) As UShort

Parametri

Restituisce

Attributi

CLSCompliantAttribute

Origine:

Interlocked.cs

Origine:

Interlocked.cs

Origine:

Interlocked.cs

public:
 static float CompareExchange(float % location1, float value, float comparand);

public static float CompareExchange (ref float location1, float value, float comparand);

static member CompareExchange : single * single * single -> single

Public Shared Function CompareExchange (ByRef location1 As Single, value As Single, comparand As Single) As Single

Parametri

Restituisce

Valore originale in location1.

Eccezioni

Esempio

Nell'esempio di codice seguente viene illustrato un metodo thread-safe che accumula un totale Single di valori in esecuzione. Due thread aggiungono una serie di Single valori usando il metodo thread-safe e l'aggiunta comune e quando i thread completano i totali vengono confrontati. In un computer a doppio processore esiste una differenza significativa nei totali.

Nel metodo thread-safe il valore iniziale del totale in esecuzione viene salvato e quindi il CompareExchange metodo viene usato per scambiare il totale appena calcolato con il totale precedente. Se il valore restituito non è uguale al valore salvato del totale in esecuzione, un altro thread ha aggiornato il totale nel frattempo. In questo caso, è necessario ripetere il tentativo di aggiornamento del totale in esecuzione.

// This example demonstrates a thread-safe method that adds to a
// running total.  
using System;
using System.Threading;

public class ThreadSafe
{
    // Field totalValue contains a running total that can be updated
    // by multiple threads. It must be protected from unsynchronized 
    // access.
    private float totalValue = 0.0F;

    // The Total property returns the running total.
    public float Total { get { return totalValue; }}

    // AddToTotal safely adds a value to the running total.
    public float AddToTotal(float addend)
    {
        float initialValue, computedValue;
        do
        {
            // Save the current running total in a local variable.
            initialValue = totalValue;

            // Add the new value to the running total.
            computedValue = initialValue + addend;

            // CompareExchange compares totalValue to initialValue. If
            // they are not equal, then another thread has updated the
            // running total since this loop started. CompareExchange
            // does not update totalValue. CompareExchange returns the
            // contents of totalValue, which do not equal initialValue,
            // so the loop executes again.
        }
        while (initialValue != Interlocked.CompareExchange(ref totalValue, 
            computedValue, initialValue));
        // If no other thread updated the running total, then 
        // totalValue and initialValue are equal when CompareExchange
        // compares them, and computedValue is stored in totalValue.
        // CompareExchange returns the value that was in totalValue
        // before the update, which is equal to initialValue, so the 
        // loop ends.

        // The function returns computedValue, not totalValue, because
        // totalValue could be changed by another thread between
        // the time the loop ends and the function returns.
        return computedValue;
    }
}

public class Test
{
    // Create an instance of the ThreadSafe class to test.
    private static ThreadSafe ts = new ThreadSafe();
    private static float control;

    private static Random r = new Random();
    private static ManualResetEvent mre = new ManualResetEvent(false);

    public static void Main()
    {
        // Create two threads, name them, and start them. The
        // thread will block on mre.
        Thread t1 = new Thread(TestThread);
        t1.Name = "Thread 1";
        t1.Start();
        Thread t2 = new Thread(TestThread);
        t2.Name = "Thread 2";
        t2.Start();

        // Now let the threads begin adding random numbers to 
        // the total.
        mre.Set();
        
        // Wait until all the threads are done.
        t1.Join();
        t2.Join();

        Console.WriteLine("Thread safe: {0}  Ordinary float: {1}", 
            ts.Total, control);
    }

    private static void TestThread()
    {
        // Wait until the signal.
        mre.WaitOne();

        for(int i = 1; i <= 1000000; i++)
        {
            // Add to the running total in the ThreadSafe instance, and
            // to an ordinary float.
            //
            float testValue = (float) r.NextDouble();
            control += testValue;
            ts.AddToTotal(testValue);
        }
    }
}

/* On a dual-processor computer, this code example produces output 
   similar to the following:

Thread safe: 17039.57  Ordinary float: 15706.44
 */

' This example demonstrates a thread-safe method that adds to a
' running total.  
Imports System.Threading

Public Class ThreadSafe
    ' Field totalValue contains a running total that can be updated
    ' by multiple threads. It must be protected from unsynchronized 
    ' access.
    Private totalValue As Single = 0.0

    ' The Total property returns the running total.
    Public ReadOnly Property Total As Single
        Get
            Return totalValue
        End Get
    End Property

    ' AddToTotal safely adds a value to the running total.
    Public Function AddToTotal(ByVal addend As Single) As Single
        Dim initialValue, computedValue As Single
        Do
            ' Save the current running total in a local variable.
            initialValue = totalValue

            ' Add the new value to the running total.
            computedValue = initialValue + addend

            ' CompareExchange compares totalValue to initialValue. If
            ' they are not equal, then another thread has updated the
            ' running total since this loop started. CompareExchange
            ' does not update totalValue. CompareExchange returns the
            ' contents of totalValue, which do not equal initialValue,
            ' so the loop executes again.
        Loop While initialValue <> Interlocked.CompareExchange( _
            totalValue, computedValue, initialValue)
        ' If no other thread updated the running total, then 
        ' totalValue and initialValue are equal when CompareExchange
        ' compares them, and computedValue is stored in totalValue.
        ' CompareExchange returns the value that was in totalValue
        ' before the update, which is equal to initialValue, so the 
        ' loop ends.

        ' The function returns computedValue, not totalValue, because
        ' totalValue could be changed by another thread between
        ' the time the loop ends and the function returns.
        Return computedValue
    End Function
End Class

Public Class Test
    ' Create an instance of the ThreadSafe class to test.
    Private Shared ts As New ThreadSafe()
    Private Shared control As Single

    Private Shared r As New Random()
    Private Shared mre As New ManualResetEvent(false)

    <MTAThread> _
    Public Shared Sub Main()
        ' Create two threads, name them, and start them. The
        ' threads will block on mre.
        Dim t1 As New Thread(AddressOf TestThread)
        t1.Name = "Thread 1"
        t1.Start()
        Dim t2 As New Thread(AddressOf TestThread)
        t2.Name = "Thread 2"
        t2.Start()

        ' Now let the threads begin adding random numbers to 
        ' the total.
        mre.Set()
        
        ' Wait until all the threads are done.
        t1.Join()
        t2.Join()

        Console.WriteLine("Thread safe: {0}  Ordinary Single: {1}", ts.Total, control)
    End Sub

    Private Shared Sub TestThread()
        ' Wait until the signal.
        mre.WaitOne()

        For i As Integer = 1 to 1000000
            ' Add to the running total in the ThreadSafe instance, and
            ' to an ordinary Single.
            '
            Dim testValue As Single = r.NextDouble()
            control += testValue
            ts.AddToTotal(testValue)
        Next
    End Sub
End Class

' On a dual-processor computer, this code example produces output 
' similar to the following:
'
'Thread safe: 17039.57  Ordinary Single: 15706.44

Commenti

Se comparand e il valore in location1 sono uguali, viene value archiviato in location1. In caso contrario, non viene eseguita alcuna operazione. Le operazioni di confronto e scambio vengono eseguite come operazione atomica. Il valore restituito di CompareExchange è il valore originale in location1, indipendentemente dal fatto che lo scambio venga eseguito.

Vedi anche

• Threading gestito
• Panoramica delle primitive di sincronizzazione

Origine:

Interlocked.cs

Origine:

Interlocked.cs

Origine:

Interlocked.CoreCLR.cs

public:
 static System::Object ^ CompareExchange(System::Object ^ % location1, System::Object ^ value, System::Object ^ comparand);

public static object CompareExchange (ref object location1, object value, object comparand);

public static object? CompareExchange (ref object? location1, object? value, object? comparand);

static member CompareExchange : obj * obj * obj -> obj

Public Shared Function CompareExchange (ByRef location1 As Object, value As Object, comparand As Object) As Object

Parametri

Restituisce

Valore originale in location1.

Eccezioni

Commenti

Se comparand e l'oggetto in location1 sono uguali per riferimento, viene value archiviato in location1. In caso contrario, non viene eseguita alcuna operazione. Le operazioni di confronto e scambio vengono eseguite come operazione atomica. Il valore restituito di CompareExchange è il valore originale in location1, indipendentemente dal fatto che lo scambio venga eseguito.

Vedi anche

• Threading gestito
• Panoramica delle primitive di sincronizzazione

public:
 static System::SByte CompareExchange(System::SByte % location1, System::SByte value, System::SByte comparand);

[System.CLSCompliant(false)]
public static sbyte CompareExchange (ref sbyte location1, sbyte value, sbyte comparand);

[<System.CLSCompliant(false)>]
static member CompareExchange : sbyte * sbyte * sbyte -> sbyte

Public Shared Function CompareExchange (ByRef location1 As SByte, value As SByte, comparand As SByte) As SByte

Parametri

Restituisce

Attributi

CLSCompliantAttribute

Origine:

Interlocked.cs

Origine:

Interlocked.cs

Origine:

Interlocked.CoreCLR.cs

public:
 static long CompareExchange(long % location1, long value, long comparand);

public static long CompareExchange (ref long location1, long value, long comparand);

static member CompareExchange : int64 * int64 * int64 -> int64

Public Shared Function CompareExchange (ByRef location1 As Long, value As Long, comparand As Long) As Long

Parametri

Restituisce

Valore originale in location1.

Eccezioni

Commenti

Se comparand e il valore in location1 sono uguali, viene value archiviato in location1. In caso contrario, non viene eseguita alcuna operazione. Le operazioni di confronto e scambio vengono eseguite come operazione atomica. Il valore restituito di CompareExchange è il valore originale in location1, indipendentemente dal fatto che lo scambio venga eseguito.

Vedi anche

• Threading gestito
• Panoramica delle primitive di sincronizzazione

Origine:

Interlocked.cs

Origine:

Interlocked.cs

Origine:

Interlocked.CoreCLR.cs

public:
 static int CompareExchange(int % location1, int value, int comparand);

public static int CompareExchange (ref int location1, int value, int comparand);

static member CompareExchange : int * int * int -> int

Public Shared Function CompareExchange (ByRef location1 As Integer, value As Integer, comparand As Integer) As Integer

Parametri

Restituisce

Valore originale in location1.

Eccezioni

Esempio

Nell'esempio di codice seguente viene illustrato un metodo thread-safe che accumula un totale in esecuzione. Il valore iniziale del totale in esecuzione viene salvato e quindi viene usato il CompareExchange metodo per scambiare il totale appena calcolato con il totale precedente. Se il valore restituito non è uguale al valore salvato del totale in esecuzione, un altro thread ha aggiornato il totale nel frattempo. In questo caso, è necessario ripetere il tentativo di aggiornamento del totale in esecuzione.

// This example demonstrates a thread-safe method that adds to a
// running total.  It cannot be run directly.  You can compile it
// as a library, or add the class to a project.
#using <system.dll>

using namespace System::Threading;
public ref class ThreadSafe
{
private:

   // totalValue contains a running total that can be updated
   // by multiple threads. It must be protected from unsynchronized 
   // access.
   int totalValue;

public:

   property int Total 
   {

      // The Total property returns the running total.
      int get()
      {
         return totalValue;
      }

   }

   // AddToTotal safely adds a value to the running total.
   int AddToTotal( int addend )
   {
      int initialValue;
      int computedValue;
      do
      {
         
         // Save the current running total in a local variable.
         initialValue = totalValue;
         
         // Add the new value to the running total.
         computedValue = initialValue + addend;
         
         // CompareExchange compares totalValue to initialValue. If
         // they are not equal, then another thread has updated the
         // running total since this loop started. CompareExchange
         // does not update totalValue. CompareExchange returns the
         // contents of totalValue, which do not equal initialValue,
         // so the loop executes again.
      }
      while ( initialValue != Interlocked::CompareExchange( totalValue, computedValue, initialValue ) );

      
      // If no other thread updated the running total, then 
      // totalValue and initialValue are equal when CompareExchange
      // compares them, and computedValue is stored in totalValue.
      // CompareExchange returns the value that was in totalValue
      // before the update, which is equal to initialValue, so the 
      // loop ends.
      // The function returns computedValue, not totalValue, because
      // totalValue could be changed by another thread between
      // the time the loop ends and the function returns.
      return computedValue;
   }

};

// This example demonstrates a thread-safe method that adds to a
// running total.  It cannot be run directly.  You can compile it
// as a library, or add the class to a project.
using System.Threading;

public class ThreadSafe {
    // totalValue contains a running total that can be updated
    // by multiple threads. It must be protected from unsynchronized 
    // access.
    private int totalValue = 0;

    // The Total property returns the running total.
    public int Total {
        get { return totalValue; }
    }

    // AddToTotal safely adds a value to the running total.
    public int AddToTotal(int addend) {
        int initialValue, computedValue;
        do {
            // Save the current running total in a local variable.
            initialValue = totalValue;

            // Add the new value to the running total.
            computedValue = initialValue + addend;

            // CompareExchange compares totalValue to initialValue. If
            // they are not equal, then another thread has updated the
            // running total since this loop started. CompareExchange
            // does not update totalValue. CompareExchange returns the
            // contents of totalValue, which do not equal initialValue,
            // so the loop executes again.
        } while (initialValue != Interlocked.CompareExchange(
            ref totalValue, computedValue, initialValue));
        // If no other thread updated the running total, then 
        // totalValue and initialValue are equal when CompareExchange
        // compares them, and computedValue is stored in totalValue.
        // CompareExchange returns the value that was in totalValue
        // before the update, which is equal to initialValue, so the 
        // loop ends.

        // The function returns computedValue, not totalValue, because
        // totalValue could be changed by another thread between
        // the time the loop ends and the function returns.
        return computedValue;
    }
}

' This example demonstrates a thread-safe method that adds to a
' running total.  It cannot be run directly.  You can compile it
' as a library, or add the class to a project.
Imports System.Threading

Public Class ThreadSafe
    ' Field totalValue contains a running total that can be updated
    ' by multiple threads. It must be protected from unsynchronized 
    ' access.
    Private totalValue As Integer = 0

    ' The Total property returns the running total.
    Public ReadOnly Property Total As Integer
        Get
            Return totalValue
        End Get
    End Property

    ' AddToTotal safely adds a value to the running total.
    Public Function AddToTotal(ByVal addend As Integer) As Integer
        Dim initialValue, computedValue As Integer
        Do
            ' Save the current running total in a local variable.
            initialValue = totalValue

            ' Add the new value to the running total.
            computedValue = initialValue + addend

            ' CompareExchange compares totalValue to initialValue. If
            ' they are not equal, then another thread has updated the
            ' running total since this loop started. CompareExchange
            ' does not update totalValue. CompareExchange returns the
            ' contents of totalValue, which do not equal initialValue,
            ' so the loop executes again.
        Loop While initialValue <> Interlocked.CompareExchange( _
            totalValue, computedValue, initialValue)
        ' If no other thread updated the running total, then 
        ' totalValue and initialValue are equal when CompareExchange
        ' compares them, and computedValue is stored in totalValue.
        ' CompareExchange returns the value that was in totalValue
        ' before the update, which is equal to initialValue, so the 
        ' loop ends.

        ' The function returns computedValue, not totalValue, because
        ' totalValue could be changed by another thread between
        ' the time the loop ends and the function returns.
        Return computedValue
    End Function
End Class

Commenti

Se comparand e il valore in location1 sono uguali, viene value archiviato in location1. In caso contrario, non viene eseguita alcuna operazione. Le operazioni di confronto e scambio vengono eseguite come operazione atomica. Il valore restituito di CompareExchange è il valore originale in location1, indipendentemente dal fatto che lo scambio venga eseguito.

Vedi anche

• Threading gestito
• Panoramica delle primitive di sincronizzazione

public:
 static short CompareExchange(short % location1, short value, short comparand);

public static short CompareExchange (ref short location1, short value, short comparand);

static member CompareExchange : int16 * int16 * int16 -> int16

Public Shared Function CompareExchange (ByRef location1 As Short, value As Short, comparand As Short) As Short

Parametri

Restituisce

Origine:

Interlocked.cs

Origine:

Interlocked.cs

Origine:

Interlocked.cs

public:
 static double CompareExchange(double % location1, double value, double comparand);

public static double CompareExchange (ref double location1, double value, double comparand);

static member CompareExchange : double * double * double -> double

Public Shared Function CompareExchange (ByRef location1 As Double, value As Double, comparand As Double) As Double

Parametri

Restituisce

Valore originale in location1.

Eccezioni

Esempio

Nell'esempio di codice seguente viene illustrato un metodo thread-safe che accumula un totale Double di valori in esecuzione. Due thread aggiungono una serie di Double valori usando il metodo thread-safe e l'aggiunta comune e quando i thread completano i totali vengono confrontati. In un computer a doppio processore esiste una differenza significativa nei totali.

Nel metodo thread-safe il valore iniziale del totale in esecuzione viene salvato e quindi il CompareExchange metodo viene usato per scambiare il totale appena calcolato con il totale precedente. Se il valore restituito non è uguale al valore salvato del totale in esecuzione, un altro thread ha aggiornato il totale nel frattempo. In questo caso, è necessario ripetere il tentativo di aggiornamento del totale in esecuzione.

// This example demonstrates a thread-safe method that adds to a
// running total.  
using System;
using System.Threading;

public class ThreadSafe
{
    // Field totalValue contains a running total that can be updated
    // by multiple threads. It must be protected from unsynchronized 
    // access.
    private double totalValue = 0.0;

    // The Total property returns the running total.
    public double Total { get { return totalValue; }}

    // AddToTotal safely adds a value to the running total.
    public double AddToTotal(double addend)
    {
        double initialValue, computedValue;
        do
        {
            // Save the current running total in a local variable.
            initialValue = totalValue;

            // Add the new value to the running total.
            computedValue = initialValue + addend;

            // CompareExchange compares totalValue to initialValue. If
            // they are not equal, then another thread has updated the
            // running total since this loop started. CompareExchange
            // does not update totalValue. CompareExchange returns the
            // contents of totalValue, which do not equal initialValue,
            // so the loop executes again.
        }
        while (initialValue != Interlocked.CompareExchange(ref totalValue, 
            computedValue, initialValue));
        // If no other thread updated the running total, then 
        // totalValue and initialValue are equal when CompareExchange
        // compares them, and computedValue is stored in totalValue.
        // CompareExchange returns the value that was in totalValue
        // before the update, which is equal to initialValue, so the 
        // loop ends.

        // The function returns computedValue, not totalValue, because
        // totalValue could be changed by another thread between
        // the time the loop ends and the function returns.
        return computedValue;
    }
}

public class Test
{
    // Create an instance of the ThreadSafe class to test.
    private static ThreadSafe ts = new ThreadSafe();
    private static double control;

    private static Random r = new Random();
    private static ManualResetEvent mre = new ManualResetEvent(false);

    public static void Main()
    {
        // Create two threads, name them, and start them. The
        // thread will block on mre.
        Thread t1 = new Thread(TestThread);
        t1.Name = "Thread 1";
        t1.Start();
        Thread t2 = new Thread(TestThread);
        t2.Name = "Thread 2";
        t2.Start();

        // Now let the threads begin adding random numbers to 
        // the total.
        mre.Set();
        
        // Wait until all the threads are done.
        t1.Join();
        t2.Join();

        Console.WriteLine("Thread safe: {0}  Ordinary Double: {1}", 
            ts.Total, control);
    }

    private static void TestThread()
    {
        // Wait until the signal.
        mre.WaitOne();

        for(int i = 1; i <= 1000000; i++)
        {
            // Add to the running total in the ThreadSafe instance, and
            // to an ordinary double.
            //
            double testValue = r.NextDouble();
            control += testValue;
            ts.AddToTotal(testValue);
        }
    }
}

/* On a dual-processor computer, this code example produces output 
   similar to the following:

Thread safe: 998068.049623744  Ordinary Double: 759775.417190589
 */

' This example demonstrates a thread-safe method that adds to a
' running total.  
Imports System.Threading

Public Class ThreadSafe
    ' Field totalValue contains a running total that can be updated
    ' by multiple threads. It must be protected from unsynchronized 
    ' access.
    Private totalValue As Double = 0.0

    ' The Total property returns the running total.
    Public ReadOnly Property Total As Double
        Get
            Return totalValue
        End Get
    End Property

    ' AddToTotal safely adds a value to the running total.
    Public Function AddToTotal(ByVal addend As Double) As Double
        Dim initialValue, computedValue As Double
        Do
            ' Save the current running total in a local variable.
            initialValue = totalValue

            ' Add the new value to the running total.
            computedValue = initialValue + addend

            ' CompareExchange compares totalValue to initialValue. If
            ' they are not equal, then another thread has updated the
            ' running total since this loop started. CompareExchange
            ' does not update totalValue. CompareExchange returns the
            ' contents of totalValue, which do not equal initialValue,
            ' so the loop executes again.
        Loop While initialValue <> Interlocked.CompareExchange( _
            totalValue, computedValue, initialValue)
        ' If no other thread updated the running total, then 
        ' totalValue and initialValue are equal when CompareExchange
        ' compares them, and computedValue is stored in totalValue.
        ' CompareExchange returns the value that was in totalValue
        ' before the update, which is equal to initialValue, so the 
        ' loop ends.

        ' The function returns computedValue, not totalValue, because
        ' totalValue could be changed by another thread between
        ' the time the loop ends and the function returns.
        Return computedValue
    End Function
End Class

Public Class Test
    ' Create an instance of the ThreadSafe class to test.
    Private Shared ts As New ThreadSafe()
    Private Shared control As Double

    Private Shared r As New Random()
    Private Shared mre As New ManualResetEvent(false)

    <MTAThread> _
    Public Shared Sub Main()
        ' Create two threads, name them, and start them. The
        ' threads will block on mre.
        Dim t1 As New Thread(AddressOf TestThread)
        t1.Name = "Thread 1"
        t1.Start()
        Dim t2 As New Thread(AddressOf TestThread)
        t2.Name = "Thread 2"
        t2.Start()

        ' Now let the threads begin adding random numbers to 
        ' the total.
        mre.Set()
        
        ' Wait until all the threads are done.
        t1.Join()
        t2.Join()

        Console.WriteLine("Thread safe: {0}  Ordinary Double: {1}", ts.Total, control)
    End Sub

    Private Shared Sub TestThread()
        ' Wait until the signal.
        mre.WaitOne()

        For i As Integer = 1 to 1000000
            ' Add to the running total in the ThreadSafe instance, and
            ' to an ordinary double.
            '
            Dim testValue As Double = r.NextDouble
            control += testValue
            ts.AddToTotal(testValue)
        Next
    End Sub
End Class

' On a dual-processor computer, this code example produces output 
' similar to the following:
'
'Thread safe: 998068.049623744  Ordinary Double: 759775.417190589

Commenti

Se comparand e il valore in location1 sono uguali, viene value archiviato in location1. In caso contrario, non viene eseguita alcuna operazione. Le operazioni di confronto e scambio vengono eseguite come operazione atomica. Il valore restituito di CompareExchange è il valore originale in location1, indipendentemente dal fatto che lo scambio venga eseguito.

Vedi anche

• Threading gestito
• Panoramica delle primitive di sincronizzazione

public:
 static System::Byte CompareExchange(System::Byte % location1, System::Byte value, System::Byte comparand);

public static byte CompareExchange (ref byte location1, byte value, byte comparand);

static member CompareExchange : byte * byte * byte -> byte

Public Shared Function CompareExchange (ByRef location1 As Byte, value As Byte, comparand As Byte) As Byte

Parametri

Restituisce

Origine:

Interlocked.cs

Origine:

Interlocked.cs

Origine:

Interlocked.cs

public:
 static IntPtr CompareExchange(IntPtr % location1, IntPtr value, IntPtr comparand);

public static IntPtr CompareExchange (ref IntPtr location1, IntPtr value, IntPtr comparand);

static member CompareExchange : nativeint * nativeint * nativeint -> nativeint

Public Shared Function CompareExchange (ByRef location1 As IntPtr, value As IntPtr, comparand As IntPtr) As IntPtr

Parametri

Restituisce

Valore originale in location1.

Eccezioni

Commenti

Se comparand e il valore in location1 sono uguali, viene value archiviato in location1. In caso contrario, non viene eseguita alcuna operazione. Le operazioni di confronto e scambio vengono eseguite come operazione atomica. Il valore restituito di questo metodo è il valore originale in location1, indipendentemente dal fatto che lo scambio venga eseguito.

Vedi anche

• Threading gestito
• Panoramica delle primitive di sincronizzazione

Origine:

Interlocked.CoreCLR.cs

Origine:

Interlocked.CoreCLR.cs

Origine:

Interlocked.CoreCLR.cs

public:
generic <typename T>
 where T : class static T CompareExchange(T % location1, T value, T comparand);

public static T CompareExchange<T> (ref T location1, T value, T comparand) where T : class;

[System.Runtime.InteropServices.ComVisible(false)]
public static T CompareExchange<T> (ref T location1, T value, T comparand) where T : class;

static member CompareExchange : 'T * 'T * 'T -> 'T (requires 'T : null)

[<System.Runtime.InteropServices.ComVisible(false)>]
static member CompareExchange : 'T * 'T * 'T -> 'T (requires 'T : null)

Public Shared Function CompareExchange(Of T As Class) (ByRef location1 As T, value As T, comparand As T) As T

Parametri di tipo

Parametri

Restituisce

Valore originale in location1.

Attributi

ComVisibleAttribute

Eccezioni

Commenti

Se comparand e il valore in location1 sono uguali per riferimento, viene value archiviato in location1. In caso contrario, non viene eseguita alcuna operazione. Il confronto e lo scambio vengono eseguiti come operazione atomica. Il valore restituito di questo metodo è il valore originale in location1, indipendentemente dal fatto che lo scambio venga eseguito.

Questo metodo supporta solo i tipi di riferimento. Esistono overload del CompareExchange metodo per i tipi di valore , SingleInt64IntPtre , Doublema non è disponibile alcun supporto per altri tipi Int32di valore.