Exception Handling on async tasks whenall

Question

I am using Using async/await for multiple tasks as reference.

public async Task DoWork() {

    int[] ids = new[] { 1, 2, 3, 4, 5 };
    await Task.WhenAll(ids.Select(i => DoSomething(1, i, blogClient)));
}

Is it possible to catch an exception on the specific index. As in, when DoSomething throws an exception on i, I can catch that specific index?

If there isn't, you can have your individual DoSomething functions throw an exception with the index as part of the data, then catch it at the DoWork level — Prodigle, Feb 13 '19 at 15:33
Possible duplicate of [Task WhenAll exception handling](https://stackoverflow.com/questions/52675789/task-whenall-exception-handling) — demo, Feb 13 '19 at 15:34

score 0 · Accepted Answer · answered Feb 13 '19 at 15:42

A simple approach is to catch the Exception, insert the index information on the exception's Data, and rethrow :

int[] ids = new[] {1, 2, 3, 4, 5};
await Task.WhenAll(ids.Select(i =>
{
    try
    {
        return DoSomething(1, i, null);
    }

    catch (Exception ex)
    {
        ex.Data["FailedIndex"] = i; // Information about failed index
        throw;
    }
}));

Exception Handling on async tasks whenall

1 Answers1