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Hashtable.IsSynchronized 屬性

定義

取得值,這個值表示對 Hashtable 的存取是否同步 (安全執行緒)。

public:
 virtual property bool IsSynchronized { bool get(); };
public virtual bool IsSynchronized { get; }
member this.IsSynchronized : bool
Public Overridable ReadOnly Property IsSynchronized As Boolean

屬性值

如果 true 的存取為同步 (安全執行緒),則為 Hashtable,否則為 false。 預設為 false

實作

範例

下列範例示範如何同步處理 Hashtable、判斷 是否已 Hashtable 同步處理 ,以及使用已同步處理的 Hashtable

#using <system.dll>

using namespace System;
using namespace System::Collections;
void main()
{
   
   // Creates and initializes a new Hashtable.
   Hashtable^ myHT = gcnew Hashtable;
   myHT->Add( (int^)0, "zero" );
   myHT->Add( 1, "one" );
   myHT->Add( 2, "two" );
   myHT->Add( 3, "three" );
   myHT->Add( 4, "four" );
   
   // Creates a synchronized wrapper around the Hashtable.
   Hashtable^ mySyncdHT = Hashtable::Synchronized( myHT );
   
   // Displays the sychronization status of both Hashtables.
   Console::WriteLine( "myHT is {0}.", myHT->IsSynchronized ? (String^)"synchronized" : "not synchronized" );
   Console::WriteLine( "mySyncdHT is {0}.", mySyncdHT->IsSynchronized ? (String^)"synchronized" : "not synchronized" );
}

/*
 This code produces the following output.

 myHT is not synchronized.
 mySyncdHT is synchronized.
 */
using System;
using System.Collections;

public class SamplesHashtable2
{
    public static void Main()
    {
        // Creates and initializes a new Hashtable.
        var myHT = new Hashtable();
        myHT.Add(0, "zero");
        myHT.Add(1, "one");
        myHT.Add(2, "two");
        myHT.Add(3, "three");
        myHT.Add(4, "four");

        // Creates a synchronized wrapper around the Hashtable.
        Hashtable mySyncdHT = Hashtable.Synchronized(myHT);

        // Displays the sychronization status of both Hashtables.
        Console.WriteLine("myHT is {0}.", myHT.IsSynchronized ? "synchronized" : "not synchronized");
        Console.WriteLine("mySyncdHT is {0}.", mySyncdHT.IsSynchronized ? "synchronized" : "not synchronized");
    }
}

/*
This code produces the following output.

myHT is not synchronized.
mySyncdHT is synchronized.
*/
Imports System.Collections

Public Class SamplesHashtable    
    
    Public Shared Sub Main()
        
        ' Creates and initializes a new Hashtable.
        Dim myHT As New Hashtable()
        myHT.Add(0, "zero")
        myHT.Add(1, "one")
        myHT.Add(2, "two")
        myHT.Add(3, "three")
        myHT.Add(4, "four")
        
        ' Creates a synchronized wrapper around the Hashtable.
        Dim mySyncdHT As Hashtable = Hashtable.Synchronized(myHT)
        
        ' Displays the sychronization status of both Hashtables.
        Dim msg As String = If(myHT.IsSynchronized, "synchronized", "not synchronized")
        Console.WriteLine($"myHT is {msg}.")
        msg = If(mySyncdHT.IsSynchronized, "synchronized", "not synchronized")
        Console.WriteLine($"mySyncdHT is {msg}.")
    End Sub
End Class

' This code produces the following output.
' 
' myHT is not synchronized.
' mySyncdHT is synchronized.

備註

Hashtable可以同時支援一個寫入器和多個讀取器。 若要支援多個寫入器,所有作業都必須透過 方法傳回的 Synchronized 包裝函式來完成。

透過集合列舉本質上不是安全線程程式。 即使集合經過同步化,其他的執行緒仍可修改該集合,使列舉值擲回例外狀況。 若要保證列舉過程的執行緒安全,您可以在整個列舉過程中鎖定集合,或攔截由其他執行緒的變更所造成的例外狀況。

下列程式代碼範例示範如何在整個列舉期間使用 SyncRoot 鎖定集合:

Hashtable^ myCollection = gcnew Hashtable();
bool lockTaken = false;

try
{
    Monitor::Enter(myCollection->SyncRoot, lockTaken);
    for each (Object^ item in myCollection)
    {
        // Insert your code here.
    }
}
finally
{
    if (lockTaken)
    {
        Monitor::Exit(myCollection->SyncRoot);
    }
}
var myCollection = new Hashtable();
lock (myCollection.SyncRoot)
{
    foreach (object item in myCollection)
    {
        // Insert your code here.
    }
}
Dim myCollection As New Hashtable()
SyncLock myCollection.SyncRoot
    For Each item In myCollection
        ' Insert your code here.
    Next
End SyncLock

適用於

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