How to get Synchronize access to the StringCollection in C#

The StringCollection class in C# is not thread-safe by default. To achieve synchronized access in multi-threaded environments, you can use the SyncRoot property combined with a lock statement to ensure thread-safe operations.

The SyncRoot property returns an object that can be used to synchronize access to the collection, preventing multiple threads from modifying or accessing the collection simultaneously.

Syntax

Following is the syntax for synchronized access to StringCollection −

lock(stringCollection.SyncRoot) {
   // thread-safe operations on stringCollection
}

Why Synchronization is Needed

In multi-threaded applications, multiple threads may try to access or modify a collection simultaneously, which can lead to data corruption or unexpected behavior. The lock statement ensures that only one thread can access the collection at a time within the locked block.

Using SyncRoot for Thread-Safe Access

Example 1

using System;
using System.Collections.Specialized;

public class Demo {
   public static void Main() {
      StringCollection stringCol = new StringCollection();
      String[] arr = new String[] { "100", "200", "300", "400", "500" };
      
      Console.WriteLine("Array elements...");
      foreach (string res in arr) {
         Console.WriteLine(res);
      }
      
      stringCol.AddRange(arr);
      Console.WriteLine("Total number of elements = " + stringCol.Count);
      stringCol.RemoveAt(3);
      Console.WriteLine("Total number of elements now = " + stringCol.Count);
      
      Console.WriteLine("Synchronize access...");
      lock(stringCol.SyncRoot) {
         foreach(object ob in stringCol) {
            Console.WriteLine(ob);
         }
      }
   }
}

The output of the above code is −

Array elements...
100
200
300
400
500
Total number of elements = 5
Total number of elements now = 4
Synchronize access...
100
200
300
500

Example 2

using System;
using System.Collections.Specialized;

public class Demo {
   public static void Main() {
      StringCollection strCol = new StringCollection();
      strCol.Add("Katie");
      strCol.Add("Philips");
      strCol.Add("Jacob");
      strCol.Add("Carl");
      strCol.Add("Gary");
      
      Console.WriteLine("Synchronize access...");
      lock(strCol.SyncRoot) {
         foreach(object ob in strCol) {
            Console.WriteLine(ob);
         }
      }
   }
}

The output of the above code is −

Synchronize access...
Katie
Philips
Jacob
Carl
Gary

Thread-Safe Operations Example

Example 3

using System;
using System.Collections.Specialized;

public class Demo {
   public static void Main() {
      StringCollection collection = new StringCollection();
      collection.Add("Item1");
      collection.Add("Item2");
      collection.Add("Item3");
      
      Console.WriteLine("Performing synchronized operations...");
      
      // Thread-safe read operation
      lock(collection.SyncRoot) {
         Console.WriteLine("Count: " + collection.Count);
         if (collection.Contains("Item2")) {
            Console.WriteLine("Item2 found in collection");
         }
      }
      
      // Thread-safe write operation
      lock(collection.SyncRoot) {
         collection.Add("Item4");
         collection.Remove("Item1");
         Console.WriteLine("After modifications, Count: " + collection.Count);
      }
      
      // Thread-safe iteration
      lock(collection.SyncRoot) {
         Console.WriteLine("Final collection:");
         foreach(string item in collection) {
            Console.WriteLine(item);
         }
      }
   }
}

The output of the above code is −

Performing synchronized operations...
Count: 3
Item2 found in collection
After modifications, Count: 3
Final collection:
Item2
Item3
Item4

Conclusion

Using the SyncRoot property with lock statements ensures thread-safe access to StringCollection in multi-threaded environments. This approach prevents data corruption and race conditions by allowing only one thread to access the collection at a time within the synchronized block.