Hashtable::Synchronized Method (Hashtable^)

 

Returns a synchronized (thread-safe) wrapper for the Hashtable.

Namespace:   System.Collections
Assembly:  mscorlib (in mscorlib.dll)

public:
[HostProtectionAttribute(SecurityAction::LinkDemand, Synchronization = true)]
static Hashtable^ Synchronized(
	Hashtable^ table
)

Parameters

table
Type: System.Collections::Hashtable^

The Hashtable to synchronize.

Return Value

Type: System.Collections::Hashtable^

A synchronized (thread-safe) wrapper for the Hashtable.

Exception Condition
ArgumentNullException

table is null.

The Synchronized method is thread safe for multiple readers and writers. Furthermore, the synchronized wrapper ensures that there is only one writer writing at a time.

Enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

The following code example shows how to lock the collection using the SyncRoot during the entire enumeration:

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);
    }
}

This method is an O(1) operation.

The following example shows how to synchronize a Hashtable, determine if a Hashtable is synchronized, and use a synchronized 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.
 */

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
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