using System;

public class Waiter

{

    public static ValueTask<IEnumerable<TResult>> KeepTrying<TResult>(Func<IEnumerable<TResult>> func, int? expectedNumber = null, bool? expectedBool = null, bool handle result = true) where TResult : IReturnedValueFromDb

    {

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

            .AddRetry(new RetryStrategyOptions<IEnumerable<TResult>>()

                      {

                        ShouldHandle = new PredicateBuilder<IEnumerable<TResult>>().Handle<NotFoundException>()

                            .HandleResult(result => 

                            {

                                if (!handleResult)

                                    return false;

                                if (expectedNumber != null)

                                    return result.First().ReturnedNumber != expectedNumber;

                                if (expectedBool != null)

                                    return result.First().ReturnedBool != expectedBool;

                                throw new InvalidOperationException("Can not determine result");

                            }),

                          MaxRetryAttempts = 3,

                          Delay = TimeSpan.FromSeconds(2)

                      })

            .Build();

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

    }

}

​

public class SomeTests

{

    [Test]

    public async Task MyTest()

    {

        var myNumber = await Waiter.KeepTrying<DatabaseReturnValues>(() => DB.GetMyNumber("some param"), expectedNumber: 1);

        Assert.That(myNumber.First().ReturnedInteger, Is.EqualTo(1));

}