.NET Framework Task Parallel Library (TPL) Task.WhenAll
Example
var random = new Random();
IEnumerable<Task<int>> tasks = Enumerable.Range(1, 5).Select(n => Task.Run(() =>
{
Console.WriteLine("I'm task " + n);
return n;
}));
Task<int[]> task = Task.WhenAll(tasks);
int[] results = await task;
Console.WriteLine(string.Join(",", results.Select(n => n.ToString())));
// Output: 1,2,3,4,5
