C# 4 and .NET 4

synchronization ❘ 529
for (int i = 0; i < taskCount; i++)
{
Console.WriteLine("task for {0}, result: {1}", i, calcs[i].Result);
}
code snippet EventSample/Program.cs
barrier
For synchronization, .NET 4 offers the new Barrier class. Barrier is great for a scenario where work is
forked into multiple tasks, and the work needs to be joined afterward. Barrier is used for participants need
to be synchronized. While the job is active, additional participants can be added dynamically, for example,
child tasks that are created from a parent task. Participants can wait until the work is done by all the other
participants before continuing.
The sample application uses a collection containing 2,000,000 strings. Multiple tasks are used to iterate
through the collection and count the number of strings starting with a, b, c, and so on.
The method FillData() creates a collection and fills it with random strings.
public static IEnumerable FillData(int size)
{
List data = new List(size);
Random r = new Random();
for (int i = 0; i < size; i++)
{
data.Add(GetString(r));
}
return data;
}
private static string GetString(Random r)
{
StringBuilder sb = new StringBuilder(6);
for (int i = 0; i < 6; i++)
{
sb.Append((char)(r.Next(26) + 97));
}
return sb.ToString();
}
code snippet BarrierSample/Program.cs
The CalculationInTask() method defines the job that’s done by a task. With the parameter, a tuple
containing four items is received. The third parameter is a reference to the Barrier instance. When the job
is done by the task, the task removes itself from the barrier with the RemoveParticipant() method.
static int[] CalculationInTask(object p)
{
var p1 = p as Tuple;
Barrier barrier = p1.Item3;
List data = p1.Item4;
int start = p1.Item1 * p1.Item2;
int end = start + p1.Item2;
Console.WriteLine("Task {0}: partition from {1} to {2}",
Task.Current.Id, start, end);
int[] charCount = new int[26];
for (int j = start; j < end; j++)
{
char c = data[j][0];
charCount[c - 97]++;
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