iot/projects/Infrastructure/Extensions/ModelStateDictionaryExtensions.cs

using Microsoft.AspNetCore.Mvc.ModelBinding;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Globalization;
using System.Linq;
using System.Linq.Expressions;

namespace Infrastructure.Extensions
{
    public static class ModelStateDictionaryExtensions
    {
        public static void AddModelError(this ModelStateDictionary modelState, IList<ValidationResult> validationResults)
        {
            if (modelState is null)
            {
                throw new ArgumentNullException(nameof(modelState));
            }
            if (validationResults is null)
            {
                throw new ArgumentNullException(nameof(validationResults));
            }

            foreach (var item in validationResults)
            {
                if (item.MemberNames.Any())
                {
                    foreach (var key in item.MemberNames)
                    {
                        modelState.AddModelError(key, item.ErrorMessage);
                    }
                }
                else
                {
                    modelState.AddModelError("", item.ErrorMessage);
                }
            }
        }

        public static object AddModelError(this ModelStateDictionary modelState, string message, string key = "", int code = 0)
        {
            if (modelState is null)
            {
                throw new ArgumentNullException(nameof(modelState));
            }

            modelState.AddModelError(key, message);
            return new
            {
                code,
                key = string.IsNullOrEmpty(key) ? key : key.Substring(0, 1).ToLower(CultureInfo.InvariantCulture) + key.Substring(1),
                message
            };
        }

        public static object AddModelError(this ModelStateDictionary modelState, Expression<Func<object, object>> expression, string message, int code = 0)
        {
            return modelState.AddModelError(message, expression.GetPropertyName(), code);
        }
    }
}