System.ArgumentOutOfRangeException: 'Index was out of range. Must be non-negative and less than the size of the collection. (Parameter 'index')'

[Arash-Sabet]

FluentValidation version

10.0.2

ASP.NET version

.net core 3.1

Summary

The fluent validation version 9.5.4 used to be able to validate our model successfully. Upgrading to 10.0.2 results to a failure per the exception in the title of this issue.

The stack trace is per below:

at System.ThrowHelper.ThrowArgumentOutOfRange_IndexException()
at System.Collections.Generic.List1.RemoveAt(Int32 index) at FluentValidation.Internal.CollectionPropertyRule2.GetValidatorsToExecute(ValidationContext1 context) in C:\Projects\FluentValidation\src\FluentValidation\Internal\CollectionPropertyRule.cs:line 335 at FluentValidation.Internal.CollectionPropertyRule2.FluentValidation.IValidationRuleInternal.Validate(ValidationContext1 context) in C:\Projects\FluentValidation\src\FluentValidation\Internal\CollectionPropertyRule.cs:line 125 at FluentValidation.AbstractValidator1.Validate(ValidationContext1 context) in C:\Projects\FluentValidation\src\FluentValidation\AbstractValidator.cs:line 92 at FluentValidation.AbstractValidator1.Validate(T instance) in C:\Projects\FluentValidation\src\FluentValidation\AbstractValidator.cs:line 62

Steps to Reproduce

The model that used to be validated successfully by FluentValidation ver 9.5.4 looks like the following code snippet:

public class MyModel
{
		public dynamic Data { set => JData = value; }
		public JObject JData{ get; private set; }
		public bool Enable{ get; set; } = false;
		public string Id{ get; set; }
                public string[] OtherIds { get; set; }
}

Version 10.0.2 fails to validate this model. The validator's code is per below:

public class MyModelValidator  : AbstractValidator<MyModel>
{
        public MyModelValidator()
        {
            RuleFor(m=> m.JData).NotNull();
            RuleForEach(m=> m.OtherIds)
                .NotEmpty()
                .MaximumLength(100)
                .When(m=> m.OtherIds?.Any() == true);
            RuleFor(m=> m.OtherIds)
                .Must(m=> m.Count() == m.Distinct().Count())
                .When(m=> m.OtherIds?.Any() == true);
        }
}

[JeremySkinner]

Thanks, yes this is a bug. It happens when you're using RuleForEach with multiple components in the same chain, plus a condition which fails.

I've fixed the issue and pushed out 10.0.3 to nuget. Please give it a try and let me know if you run into any further issues.

[Arash-Sabet]

Thanks, @JeremySkinner for the prompt answer. The issue is now fixed. Please close this ticket.