using System;

using System.Linq;

using System.Collections.Generic;

using System.Threading.Tasks;

using Polly;

​

public class Program

{

    public static async Task Main()

    {

        await KeepTrying<A>(() => [new ()], 1); //no retry

        await KeepTrying<B>(() => [new ()], 1); //three retries

    }

    static ValueTask<IEnumerable<TResult>> KeepTrying<TResult>(

      Func<IEnumerable<TResult>> func, int expectedInteger) 

      where TResult : IMyInteger

    {

        var pipeline = new ResiliencePipelineBuilder<IEnumerable<TResult>>()

        .AddRetry(new()

        {

            ShouldHandle = new PredicateBuilder<IEnumerable<TResult>>()

                .Handle<NotFoundException>()

                .HandleResult(result => result.First().MyInteger != expectedInteger),

            MaxRetryAttempts = 3,

            Delay = TimeSpan.FromSeconds(1),

            OnRetry = static args =>

            {

                Console.WriteLine(args.Outcome.Result);

                return default;

            }

        })

        .Build();

​

        return ValueTask.FromResult(pipeline.Execute(func));

    }

}

​

interface IMyInteger

{

    public int MyInteger { get; }

}

​

class A : IMyInteger

{

    public int MyInteger { get; } = 1;

}

​

class B : IMyInteger

{

    public int MyInteger { get; } = 2;

}

​

class NotFoundException: Exception

{

}