gehgassi_backend/gehGassi.Web/Helper/RequiredIfDefaultLanguage.cs

using System;
using System.ComponentModel.DataAnnotations;
using System.Globalization;
using System.Reflection;
using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.Extensions.Localization;
using Microsoft.Extensions.Options;

namespace gehGassi.Web.Helper
{
    /// <summary>
    /// Prüft ob ein Feld angegeben werden muss, wenn es sich um die Übersetzung der Standard-Sprache ist.
    /// </summary>
    [AttributeUsage(AttributeTargets.Property, AllowMultiple = true)]
    public class RequiredIfDefaultLanguage : ValidationAttribute, IClientModelValidator
    {
        public string OtherProperty { get; }

        public RequiredIfDefaultLanguage(string otherProperty)
        {
            OtherProperty = otherProperty;
        }

        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            var localizationOptions = (IOptions<LocalizationOptions>)validationContext.GetService(typeof(IOptions<LocalizationOptions>));
            var defaultLanguage = localizationOptions.Value.DefaultCulture;

            PropertyInfo otherPropertyInfo = validationContext.ObjectType.GetProperty(OtherProperty);
            if (otherPropertyInfo == null)
            {
                return new ValidationResult($"Unknown property {OtherProperty}");
            }

            var otherLanguage = string.Empty;
            object otherValue = otherPropertyInfo.GetValue(validationContext.ObjectInstance, null);
            if (otherValue != null)
            {
                otherLanguage = otherValue.ToString();
            }
            if(otherLanguage == defaultLanguage && value == null)
                return new ValidationResult(string.Format(ErrorMessage, validationContext.DisplayName));

            var stringValue = "";
            if(value != null)
                stringValue = value.ToString();

            if (otherLanguage == defaultLanguage && string.IsNullOrWhiteSpace(stringValue))
                return new ValidationResult(string.Format(ErrorMessage, validationContext.DisplayName));

            return ValidationResult.Success;
        }

        public void AddValidation(ClientModelValidationContext context)
        {
            var localizerFactory = (IStringLocalizerFactory)context.ActionContext.HttpContext.RequestServices.GetService(typeof(IStringLocalizerFactory));
            var localizationOptions = (IOptions<LocalizationOptions>)context.ActionContext.HttpContext.RequestServices.GetService(typeof(IOptions<LocalizationOptions>));
            var defaultLanguage = localizationOptions.Value.DefaultCulture;

            var localizer = localizerFactory.Create("Annotations", "Local");

            var viewContext = context.ActionContext as ViewContext;
            var otherPropertyFullName = viewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(OtherProperty);
            var otherPropertyFullId = otherPropertyFullName.Replace(".", "_");

            var prefix = "";
            if (context.ModelMetadata.ContainerType != null && context.ModelMetadata.ContainerMetadata != null)
            {
                foreach (var propertyInfo in context.ModelMetadata.ContainerMetadata.GetType().GetProperties())
                {
                    if (propertyInfo.PropertyType == context.ModelMetadata.ContainerType)
                    {
                        prefix = propertyInfo.Name;
                        break;
                    }
                }
            }

            if (!context.Attributes.ContainsKey("data-val"))
                context.Attributes.Add("data-val", "true");
            if (!context.Attributes.ContainsKey("data-val-requiredif-defaultlangauge"))
                context.Attributes.Add("data-val-requiredif-defaultlangauge", string.Format((IFormatProvider)CultureInfo.CurrentCulture, localizer["Err_Required"], context.ModelMetadata.GetDisplayName()));
            if (!string.IsNullOrWhiteSpace(prefix))
            {
                if (!context.Attributes.ContainsKey("data-val-requiredif-defaultlangauge-other"))
                    context.Attributes.Add("data-val-requiredif-defaultlangauge-other", prefix + "." + otherPropertyFullName); // data-val-requiredif-other
            }
            else
            {
                if (!context.Attributes.ContainsKey("data-val-requiredif-defaultlangauge-other"))
                    context.Attributes.Add("data-val-requiredif-defaultlangauge-other", otherPropertyFullName); // data-val-requiredif-other
            }
            if (!context.Attributes.ContainsKey("data-val-requiredif-defaultlangauge-otherval"))
                context.Attributes.Add("data-val-requiredif-defaultlangauge-otherval", defaultLanguage); // data-val-requiredif-other
        }
    }
}