Explanation
The Task.WaitAll method (Task[]) waits for all of the provided Task objects to complete execution.
Example:
// Construct started tasks
Task<int>[] tasks = new Task<int>[n];
for (int i = 0; i < n; i++)
{
tasks[i] = Task<int>.Factory.StartNew(action, i);
}
// Exceptions thrown by tasks will be propagated to the main thread
// while it waits for the tasks. The actual exceptions will be wrapped in AggregateException.
try
{
// Wait for all the tasks to finish.
Task.WaitAll(tasks);
// We should never get to this point
Console.WriteLine("WaitAll() has not thrown exceptions. THIS WAS NOT EXPECTED.");
}
Reference: Task.WaitAll Method (Task[])
https://msdn.microsoft.com/en-us/library/dd270695(v=vs.110).aspx