c# - Await for list of Tasks

Question

I'm trying to do something like this:

foreach (var o in ObjectList) 
{ 
    CalculateIfNeedToMakeTaskForO(o);

    if (yes) 
        TaskList.Add(OTaskAsync());
}

Now I would like to wait for all these tasks to complete. Besides doing

foreach(var o in ObjectList)
{
    Result.Add("result for O is: "+await OTaskAsync());
}

Is there anything I could do? (better, more elegant, more "correct")

Answer 1

You are looking for Task.WhenAll:

var tasks = ObjectList
    .Where(o => CalculateIfNeedToMakeTaskForO(o))
    .Select(o => OTaskAsync(o))
    .ToArray();
var results = await Task.WhenAll(tasks);
var combinedResults = results.Select(r => "result for O is: " + r);