ValidatorJustSomeBadTry

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace PinP.Service
{
    public delegate bool Validation();
    public class ValidatorDtos
    {
        private List<ValidationRuleDtos> _validationRules;
        public void AddRule(ValidationRuleDtos rule) => _validationRules.Add(rule);

        public string ValidationResultByFieledName(string filedName) => _validationRules.FirstOrDefault(r => r.FieldName.Equals(filedName))?.ValidateResult() ?? string.Empty;

        public string ValidateResults() => string.Join(", ", _validationRules.Select(r => r.ValidateResult()).Where(r => !string.IsNullOrEmpty(r)));
    }
    public class ValidationRuleDtos
    {
        public string FieldName { get; set; }
        public string ErrorDescription { get; set; }
        public event Validation CustomValidation;

        public ValidationRuleDtos(string fieldName, string errorDescription)
        {
            FieldName = fieldName;
            ErrorDescription = errorDescription;
        }
        public ValidationRuleDtos(string fieldName, Func<bool> customValidation, string errorDescription)
        {
            FieldName = fieldName;
            CustomValidation += () => customValidation();
            ErrorDescription = errorDescription;
        }
        public bool Check()
        {
            if (CustomValidation != null)
            {
                return CustomValidation();
            }
            return true;
        }
        public string ValidateResult() => Check() ? string.Empty : ErrorDescription;
    }
}