ArrayList.IsSynchronized Property
Definition
Important
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Gets a value indicating whether access to the ArrayList is synchronized (thread safe).
public:
virtual property bool IsSynchronized { bool get(); };public virtual bool IsSynchronized { get; }member this.IsSynchronized : boolPublic Overridable ReadOnly Property IsSynchronized As BooleanProperty Value
true if access to the ArrayList is synchronized (thread safe); otherwise, false. The default is false.
Implements
Examples
The following code example shows how to lock the collection using the SyncRoot during the entire enumeration.
ArrayList^ myCollection = gcnew ArrayList();
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);
}
}
ArrayList myCollection = new ArrayList();
lock(myCollection.SyncRoot)
{
foreach (object item in myCollection)
{
// Insert your code here.
}
}
Dim myCollection As New ArrayList()
SyncLock myCollection.SyncRoot
For Each item As Object In myCollection
' Insert your code here.
Next item
End SyncLock
Retrieving the value of this property is an O(1) operation.
The following code example shows how to synchronize an ArrayList, determine if an ArrayList is synchronized and use a synchronized ArrayList.
using namespace System;
using namespace System::Collections;
int main()
{
// Creates and initializes a new ArrayList instance.
ArrayList^ myAL = gcnew ArrayList;
myAL->Add( "The" );
myAL->Add( "quick" );
myAL->Add( "brown" );
myAL->Add( "fox" );
// Creates a synchronized wrapper around the ArrayList.
ArrayList^ mySyncdAL = ArrayList::Synchronized( myAL );
// Displays the sychronization status of both ArrayLists.
String^ szRes = myAL->IsSynchronized ? (String^)"synchronized" : "not synchronized";
Console::WriteLine( "myAL is {0}.", szRes );
String^ szSyncRes = mySyncdAL->IsSynchronized ? (String^)"synchronized" : "not synchronized";
Console::WriteLine( "mySyncdAL is {0}.", szSyncRes );
}
/*
This code produces the following output.
myAL is not synchronized.
mySyncdAL is synchronized.
*/
using System;
using System.Collections;
public class SamplesArrayList {
public static void Main() {
// Creates and initializes a new ArrayList.
ArrayList myAL = new ArrayList();
myAL.Add( "The" );
myAL.Add( "quick" );
myAL.Add( "brown" );
myAL.Add( "fox" );
// Creates a synchronized wrapper around the ArrayList.
ArrayList mySyncdAL = ArrayList.Synchronized( myAL );
// Displays the sychronization status of both ArrayLists.
Console.WriteLine( "myAL is {0}.", myAL.IsSynchronized ? "synchronized" : "not synchronized" );
Console.WriteLine( "mySyncdAL is {0}.", mySyncdAL.IsSynchronized ? "synchronized" : "not synchronized" );
}
}
/*
This code produces the following output.
myAL is not synchronized.
mySyncdAL is synchronized.
*/
Imports System.Collections
Public Class SamplesArrayList
Public Shared Sub Main()
' Creates and initializes a new ArrayList.
Dim myAL As New ArrayList()
myAL.Add("The")
myAL.Add("quick")
myAL.Add("brown")
myAL.Add("fox")
' Creates a synchronized wrapper around the ArrayList.
Dim mySyncdAL As ArrayList = ArrayList.Synchronized(myAL)
' Displays the sychronization status of both ArrayLists.
Dim str As String
If myAL.IsSynchronized Then
str = "synchronized"
Else
str = "not synchronized"
End If
Console.WriteLine("myAL is {0}.", str)
If mySyncdAL.IsSynchronized Then
str = "synchronized"
Else
str = "not synchronized"
End If
Console.WriteLine("mySyncdAL is {0}.", str)
End Sub
End Class
' This code produces the following output.
'
' myAL is not synchronized.
' mySyncdAL is synchronized.
Remarks
To guarantee the thread safety of the ArrayList, all operations must be done through the wrapper returned by the Synchronized method.
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.
