Why would you do this?

PCLs don’t support them

Okay – How?

List<Task> myTasks = new List<Task>();

for (int i = 1; i <= 10; i++) // Artificially implement Parallel.For because this is a PCL
{
    myTasks.Add(Task.Run(() =>
    {
        // Task logic goes here
    }));
}

await Task.WhenAll(myTasks);

Small victories.