Hashtable.Synchronized(Hashtable) Method

Definition

Namespace:

System.Collections

Assemblies:

netstandard.dll, System.Runtime.dll

Source:

Hashtable.cs

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

C#

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

Parameters

table

Hashtable

The Hashtable to synchronize.

Returns

Hashtable

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

Exceptions

ArgumentNullException

table is null.

Examples

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

C#

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.
*/

Remarks

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:

C#

var myCollection = new Hashtable();
lock (myCollection.SyncRoot)
{
    foreach (object item in myCollection)
    {
        // Insert your code here.
    }
}

This method is an O(1) operation.

Applies to

See also

• IsSynchronized
• SyncRoot