Simple, but effective, asynchronous Retry mechanism with Exponential Backoff for C#

RetryWithExponentialBackoffAsync.cs

namespace CajunCoding
{
    /// <summary>
    /// Simple but effective Retry mechanism for C# with Exponential backoff and support for validating each result to determine if it should continue trying or accept the result.
    /// https://en.wikipedia.org/wiki/Exponential_backoff
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="maxRetries">The Max number of attempts that will be made.</param>
    /// <param name="action">The Func&lt;T&gt; process/action that will be attempted and will return generic type &lt;T&gt; when successful.</param>
    /// <param name="validationAction">A dynamic validation rule that can determine if a given result of generic type &lt;T&gt; is acceptable or if the action should be re-attempted.</param>
    /// <param name="initialRetryWaitTimeMillis">The initial delay time if the action fails; after which it will be exponentially expanded for longer delays with each iteration.</param>
    /// <returns>Generic type &lt;T&gt; result from the Func&lt;T&gt; action specified.</returns>
    /// <exception cref="AggregateException">Any and all exceptions that occur from all attempts made before the max number of retries was encountered.</exception>
    public class Retry
    {
        public class RetryStatus
        {
            public RetryStatus(int failedAttemptCount = 0, int maxRetryAttemptCount = 0)
            {
                FailedAttemptCount = failedAttemptCount;
                MaxRetryAttemptCount = maxRetryAttemptCount;
            }
            public int FailedAttemptCount { get; }
            public int MaxRetryAttemptCount { get; }
            public int RemainingRetryCount => MaxRetryAttemptCount - FailedAttemptCount;
            public bool StopRetryProcess { get; private set; } = false;
            public void StopRetrying() { StopRetryProcess = true; }
        }

        public static async Task<T> WithExponentialBackoffAsync<T>(
            int maxRetries,
            Func<RetryStatus, Task<T>> action,
            int initialRetryWaitTimeMillis = 1000
        )
        {
            var exceptions = new List<Exception>();
            var maxRetryValidatedCount = Math.Max(maxRetries, 1);
            //NOTE: We always make an initial attempt (index = 0, with NO delay) + the max number of retries attempts with 
            //      exponential back-off delays; so for example with a maxRetries specified of 3 + 1 for the initial
            //      we will make a total of 4 attempts!
            for (var failCount = 0; failCount <= maxRetryValidatedCount; failCount++)
            {
                var retryStatus = new RetryStatus(failCount);
                try
                {
                    //If we are retrying then we wait using an exponential back-off delay...
                    if (failCount > 0)
                    {
                        var powerFactor = Math.Pow(failCount, 2); //This is our Exponential Factor
                        var waitTimeSpan = TimeSpan.FromMilliseconds(powerFactor * initialRetryWaitTimeMillis); //Total Wait Time
                        await Task.Delay(waitTimeSpan).ConfigureAwait(false);
                    }

                    //Attempt the Action...
                    var result = await action(retryStatus).ConfigureAwait(false);
                    return result;
                }
                catch (Exception exc)
                {
                    exceptions.Add(exc);
                    if (retryStatus.StopRetryProcess)
                        break;
                }
            }

            //If we have Exceptions that were handled then we attempt to re-throw them so calling code can handle...
            switch (exceptions.Count)
            {
                case 0: break;//DO NOTHING
                case 1: throw exceptions.First();
                default: throw new AggregateException(exceptions);
            }

            //Finally if no exceptions were handled (e.g. all failures were due to validateResult Func failing them) then we return the default (e.g. null)...
            return default;
        }
    }
}

Simple Usage:

int exponentialBackoffRetryAttempts = 10; //Read from configuration...

return await Retry.WithExponentialBackoffAsync(exponentialBackoffRetryAttempts , async (retryStatus) =>
{
    var response = await service.DoSomeRequestsAsync(requestParams).ConfigureAwait(false);
    
    //... post process the response if needed...
    
    return response;
}).ConfigureAwait(false)

Advanced Usage:

int exponentialBackoffRetryAttempts = 10; //Read from configuration...
var timer = Stopwatch.StartNew();

return await Retry.WithExponentialBackoffAsync(exponentialBackoffRetryAttempts, async (retryStatus) =>
{
    var response = await service.DoSomeRequestsAsync(requestParams).ConfigureAwait(false);
    
    //Log the current retry status with details for how many attempts have been attempted, the max number, etc.
    if(retryStatus.FailedAttemptCount > 0)
        _log.LogTrace("Retrying Async Request [{ApiAttemptCount} of {MaxApiRetryCount}]...",
            retryStatus.FailedAttemptCount + 1,
            retryStatus.MaxRetryAttemptCount
        );

    //Manually stop any further retrying based on custom logic (here we halt if total time is greater than two minutes)...
    if(timer.Elapsed.TotalMinutes > 2)
        retryStatus.StopRetrying();

    return response;
}).ConfigureAwait(false)