How to get Synchronize access to the StringDictionary in C#

StringDictionary.SyncRoot Property is used to get an object which can be used to synchronize access to the StringDictionary. It only allows string keys and string values. It suffers from performance problems. It implements a hash table with the key and the value strongly typed to be strings rather than objects.

Syntax: public virtual object SyncRoot { get; }

Property Value: An object which can be used to synchronize access to the StringDictionary.

Important Points:

• Synchronization of an object is done so that only one thread can manipulate the data in the StringDictionary.
• A property is a member of a class that provides a means for reading, writing and computing private data fields.
• The synchronizing code cannot directly perform on the collection, so it must perform operations on the SyncRoot of the collection in order to guarantee the proper operation of collections that are derived from other objects.
• Retrieving the value of this property is an O(1) operation.

Below programs illustrate the use of the above-discussed property:

Example 1: In this code, we are using SyncRoot to get Synchronized access to the StringDictionary named sd, which is not a thread-safe procedure and can cause an exception. So to avoid the exception we lock the collection during the enumeration.

// C# program to illustrate the
// use of SyncRoot property of
// the StringDictionary class
using System;
using System.Threading;
using System.Collections;
using System.Collections.Specialized;

namespace sync_root {

class GFG {

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

        // Declaring an StringDictionary
        StringDictionary sd = new StringDictionary();

        // Adding elements to StringDictionary
        sd.Add("Australia", "Canberra");
        sd.Add("Belgium", "Brussels");
        sd.Add("Netherlands", "Amsterdam");
        sd.Add("China", "Beijing");
        sd.Add("Russia", "Moscow");
        sd.Add("India", "New Delhi");

        // Using the SyncRoot property
        lock(sd.SyncRoot)
        {
            // foreach loop to display
            // the elements in sd
            foreach(DictionaryEntry i in sd)
                Console.WriteLine(i.Key + " ---- " + i.Value);
        }
    }
}
}

Output:

china ---- Beijing
netherlands ---- Amsterdam
belgium ---- Brussels
australia ---- Canberra
india ---- New Delhi
russia ---- Moscow

Example 2:

// C# program to illustrate the
// use of SyncRoot property of
// the StringDictionary class
using System;
using System.Threading;
using System.Collections;
using System.Collections.Specialized;

namespace sync_root {

class GFG {

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

        // Declaring an StringDictionary
        StringDictionary sd = new StringDictionary();

        // Adding elements to StringDictionary
        sd.Add("1", "C");
        sd.Add("2", "C++");
        sd.Add("3", "Java");
        sd.Add("4", "C#");
        sd.Add("5", "HTML");

        // Using the SyncRoot property
        lock(sd.SyncRoot)
        {
            // foreach loop to display
            // the elements in sd
            foreach(DictionaryEntry i in sd)
                Console.WriteLine(i.Key + " ----> " + i.Value);
        }
    }
}
}

Output:

3 ----> Java
5 ----> HTML
4 ----> C#
2 ----> C++
1 ----> C

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.collections.specialized.stringdictionary.syncroot?view=netframework-4.7.2