Mastering C# Concurrency

Concurrent collections in .NET

Since the first .NET Framework version, most of the collections in the System.Collections namespace contained the Synchronized factory method that creates a thread safe wrapper over the collection instance, which ensures thread safety:

var source = Enumerable.Range(1, 42000).ToList();
var destination = ArrayList.Synchronized(new List<int>());
 
Parallel.ForEach(source,
    n =>
    {
        destination.Add(n);
    });
 
Assert.AreEqual(source.Count, destination.Count);

The synchronized collection wrapper can be used in a concurrent environment, but its efficiency is low, since it uses simple locking ensuring exclusive collection access for every operation. This approach is called coarse-grained locking and it is described in Chapter 3 ...