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Nested .When operations causes exception

See original GitHub issue

Which version of FluentValidation are you using? 10.0.0-preview3

Describe the issue that you’re having The following code causes an exception when the validator is instantiated

public class SomeType
{
    public bool Value1 { get; set; }

    public bool Value2 { get; set; }
}

public class SomeTypeValidator : AbstractValidator<SomeType>
{
    public SomeTypeValidator()
    {
        this.When(
                o => o.Value1,
                () =>
                {
                    // do stuff
                })
            .Otherwise(
                () =>
                {
                    this.When(
                        o => o.Value2,
                        () =>
                        {
                            // do stuff
                        });
                });
    }
}

System.ArgumentException
Delegates must be of the same type.
   at System.MulticastDelegate.CombineImpl(Delegate follow)
   at FluentValidation.Internal.TrackingCollection`1.add_ItemAdded(Action`1 value)
   at FluentValidation.Internal.TrackingCollection`1.OnItemAdded(Action`1 onItemAdded) in C:\Projects\FluentValidation\src\FluentValidation\Internal\TrackingCollection.cs:line 48
   at FluentValidation.Internal.ConditionBuilder`1.When(Func`3 predicate, Action action) in C:\Projects\FluentValidation\src\FluentValidation\Internal\ConditionBuilder.cs:line 40
   at FluentValidation.AbstractValidator`1.When(Func`3 predicate, Action action) in C:\Projects\FluentValidation\src\FluentValidation\AbstractValidator.cs:line 302
   at FluentValidation.AbstractValidator`1.When(Func`2 predicate, Action action) in C:\Projects\FluentValidation\src\FluentValidation\AbstractValidator.cs:line 292
   at Nordic.Application.Sales.Tests.StructuralRules.ElementToggling.Common.TestObjValidator.<.ctor>b__0_2() in D:\source\roadmap\src\Core\Nordic.Application.Sales.Tests\StructuralRules\ElementToggling\Common.cs:line 63
   at FluentValidation.Internal.ConditionOtherwiseBuilder`1.Otherwise(Action action) in C:\Projects\FluentValidation\src\FluentValidation\Internal\ConditionBuilder.cs:line 161

It appears that it’s trying to combine two delegates where one is Action<IValidationRule<T>> and the other is Action<IValidationRuleInternal<T>>