using System;

using System.Linq;

using System.Text.Json;

using FluentValidation;

using FluentValidation.Validators;

using FluentValidation.TestHelper;

using System.Reflection;

​

public class Program

{

    public static void Main()

    {

        UpdateRequest model = new UpdateRequest { Prop1 = null, Prop2 = null, Prop3 = null };

        var context = new ValidationContext<UpdateRequest>(model);

        context.RootContextData["MyCustomData"] = "Test";

        var _validator = new UpdateRequestValidator();

        //FluentValidation.Results.ValidationResult result = _validator.Validate(model);

        var result = _validator.TestValidate(context);

        Console.WriteLine(JsonSerializer.Serialize(result, new JsonSerializerOptions { WriteIndented = true }));

    }

}

​

public record UpdateRequest

{

    public int? Prop1 { get; init; }

    public int? Prop2 { get; init; }

    public int? Prop3 { get; init; }

}

​

public class UpdateRequestValidator : AbstractValidator<UpdateRequest>

{

    public UpdateRequestValidator()

    {

        RuleFor(x => x)

            .Cascade(CascadeMode.Stop)

            .Custom((request, context) =>

            {

                Console.WriteLine("MyCustomData", context.RootContextData["MyCustomData"]);

                var properties = request.GetType()

                    .GetProperties(BindingFlags.Public | BindingFlags.Instance)

                    .Where(p => p.PropertyType == typeof(int?))

                    .ToList();

                bool allNull = properties.All(p => ((int?)(p.GetValue(request))).GetValueOrDefault() == 0);

                bool allNotNull = properties.All(p => ((int?)(p.GetValue(request))).GetValueOrDefault() != 0);

​

                if (!(allNull || allNotNull))

                {

                    var firstPropertyWithValue = properties.First(x => x.GetValue(request) != null);

                    var propertiesWithoutValue = properties.Where(x => x.Name != firstPropertyWithValue.Name);

                    context.AddFailure(

                        String.Format("{0} cannot be 0 or null when {1} is provided.",

                            String.Join('&', propertiesWithoutValue.Select(x => x.Name)),

                            firstPropertyWithValue.Name));

                }

            });

    }

}