C# | Creating a synchronized (thread-safe) wrapper for the Hashtable

Last Updated : 09 Aug, 2021

Hashtable.Synchronized(Hashtable) Method is used to return a synchronized (thread-safe) wrapper for the Hashtable.
Syntax:

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

Here table is the Hashtable which is to be synchronized.
Return Value: This method returns a synchronized (thread-safe) wrapper for the Hashtable.
Exception: This method will throw the ArgumentNullException if the table is null.
Below programs illustrate the use of above-discussed method:
Example 1:

CSharp

// C# code to get a synchronized (thread-
// safe) wrapper for the Hashtable
using System;
using System.Collections;

class GFG {

    // Main method
    static void Main(string[] args)
    {

        // create and initialize Hash table
        // using Add() method
        Hashtable has1 = new Hashtable();
        has1.Add("1", "Welcome");
        has1.Add("2", "to");
        has1.Add("3", "geeks");
        has1.Add("4", "for");
        has1.Add("5", "geeks");

        // Creating a synchronized packing
        // around the Hashtable
        Hashtable has2 = Hashtable.Synchronized(has1);

        // --------- Using IsSynchronized Property

        // print the status of both Hashtables
        Console.WriteLine("has1 Hashtable is {0}.",
            has1.IsSynchronized ? "synchronized" : 
                              "not synchronized");

        Console.WriteLine("has2 Hashtable is {0}.",
             has2.IsSynchronized ? "synchronized" :
                               "not synchronized");
    }
}

Output:

has1 Hashtable is not synchronized.
has2 Hashtable is synchronized.

Example 2:

CSharp

// C# code to get a synchronized (thread-
// safe) wrapper for the Hashtable
using System;
using System.Collections;

class GFG {

    // Main method
    static void Main(string[] args)
    {

        // create and initialize Hash table
        // there will be no elements
        Hashtable has1 = new Hashtable();

        // it will give runtime error as
        // table parameter can't be null
        Hashtable has2 = Hashtable.Synchronized(null);
    }
}

Runtime Error:

Unhandled Exception:
System.ArgumentNullException: Value cannot be null.
Parameter name: table

Note:

This method is a 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 process. Other threads can still modify the collection, which causes the enumerator to throw an exception even when a collection is synchronized.
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.
This method is an O(1) operation.

Reference:

https://docs.microsoft.com/en-us/dotnet/api/system.collections.hashtable.synchronized?view=netframework-4.7.2

Kirti_Mangal

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C# | Creating a synchronized (thread-safe) wrapper for the Hashtable

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