Hashtable.Synchronized(Hashtable) 方法

定义

命名空间:

System.Collections

程序集:

System.Runtime.dll

Source:

Hashtable.cs

返回 Hashtable 的同步（线程安全）包装。

public:
 static System::Collections::Hashtable ^ Synchronized(System::Collections::Hashtable ^ table);

public static System.Collections.Hashtable Synchronized (System.Collections.Hashtable table);

static member Synchronized : System.Collections.Hashtable -> System.Collections.Hashtable

Public Shared Function Synchronized (table As Hashtable) As Hashtable

参数

table

Hashtable

要同步的 Hashtable。

返回

Hashtable

Hashtable 的同步（线程安全）包装。

例外

ArgumentNullException

table 为 null。

示例

以下示例演示如何同步 ， Hashtable确定 是否 Hashtable 同步，并使用同步的 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.

注解

方法 Synchronized 对多个读取器和编写器是线程安全的。 此外，同步包装器可确保一次只有一个写入器写入。

枚举整个集合本质上不是一个线程安全的过程。 即使某个集合已同步，其他线程仍可以修改该集合，这会导致枚举数引发异常。 若要确保枚举过程中的线程安全性，可以在整个枚举期间锁定集合，或者捕获由其他线程进行的更改所导致的异常。

下面的代码示例演示如何在整个枚举期间使用 SyncRoot 锁定集合：

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

此方法是一种 O(1) 操作。

另请参阅

• IsSynchronized
• SyncRoot