FluentValidation using RootContextData

Program.cs

using System.Collections.Generic;
using System.Linq;

namespace ConsoleApplication1 {
	using FluentValidation;
	using FluentValidation.Results;

	public class ParentEntity {
		public string Code { get; set; }
		public List<ChildEntity> Children { get; set; } = new List<ChildEntity>();
	}

	public class ChildEntity {
		public string Code { get; set; }
	}

	public class ParentEntityValidator : AbstractValidator<ParentEntity> {
		public ParentEntityValidator() {
			RuleFor(o => o.Children).SetCollectionValidator(new ChildEntityValidator());
			RuleFor(o => o.Code)
				.Must((entity, code, ctx) => {
					return ctx.ParentContext.RootContextData.Any(); // Not working
				})
				.WithMessage("ParentEntityValidator.RuleFor(o => o.Code).Must");
			Custom((entity, ctx) => {
				return ctx.RootContextData.Any() // Here it works!
					? null
					: new ValidationFailure("", "ParentEntityValidator.Custom");
			});
		}
	}

	public class ChildEntityValidator : AbstractValidator<ChildEntity> {
		public ChildEntityValidator() {
			RuleFor(m => m.Code)
				.Must((entity, code, ctx) => {
					return ctx.ParentContext.RootContextData.Any(); // Not working
				})
				.WithMessage("ChildEntityValidator.RuleFor(m => m.Code).Must");
			Custom((entity, ctx) => {
				return ctx.RootContextData.Any() // Not working
					? null 
					: new ValidationFailure("", "ChildEntityValidator.Custom");
			});
		}
	}

	class Program {
		static void Main(string[] args) {
			// Create entities to validate 
			var parent = new ParentEntity();
			for (var i = 0; i < 1; i++) {
				parent.Children.Add(new ChildEntity {Code = $"Code{i}"});

			}
			// Custom data
			var data = new HashSet<string>();

			// Sync
			var rootCtx = new ValidationContext<ParentEntity>(parent);
			rootCtx.RootContextData.Add("data", data);
			var result = new ParentEntityValidator().Validate(rootCtx);
			if (!result.IsValid) {
				// Does not work
			}
			// Async
			result = new ParentEntityValidator().ValidateAsync(rootCtx).Result;
			if (!result.IsValid) {
				// Does not work
			}
		}
	}
}