I have this

public static async Task Retry<T>(Func<T> action, TimeSpan retryInterval, int maxAttemptCount = 3)
{
    var exceptions = new List<Exception>();

    for (int attempted = 0; attempted < maxAttemptCount; attempted  )
    {
        try
        {
            if (attempted > 0)
            {
                Thread.Sleep(retryInterval);
            }
            return await action();
        }
        catch (Exception ex)
        {
            exceptions.Add(ex);
        }
    }
    throw new AggregateException(exceptions);
}

and try to run this by

await Retry(() => SaveFile(command, tracker.ActivityId, blobService), TimeSpan.FromSeconds(5), retryCount);

but i got error in Retry in return await action() (T does not contain definition for getAwaiter)

i need to return from the loop when action is done

and my action

Task SaveFile<TCommand>(TCommand command, string activityId, IBlobService blobService) where TCommand : DomainComman

CodePudding user response：

There are a few issues here.

1. action returns T, you cannot await this, you can only await Task or Task<T>. So if you want to await action it should have the signature Func<Task<T>>
2. Your return type is wrong. It looks like you want to return a T, then the return type should be Task<T>
3. If you are using asynchronous code you should not be using Thread.Sleep, use Task.Delay instead, and await this.

You might also want to add some logging, or a custom exception to make it clearer that this was a repeated failure. Someone looking at a aggregate exception with three duplicates might not immediately figure out what is going on.

CodePudding user response：

Async functions returns Task for beeing awaitable. So in your code you TResult is T and you need to redifine the Func<T> to Func<Task<T>>.

As you return the result of action you need also to change the return type of your function to Task<T>

So you end up with:

public static async Task Retry<T>(Func<T> action, TimeSpan retryInterval, int maxAttemptCount = 3)

as SaveFile seams also to be async so you should change the call to:

await Retry(async () => await SaveFile(command, tracker.ActivityId, blobService), TimeSpan.FromSeconds(5), retryCount);