ASP.NET Core自定义验证属性本地化

Question

我正在尝试在asp.net core 1.0中的自定义验证属性中实现本地化.这是我简化的viewmodel:

public class EditPasswordViewModel
{
    [Required(ErrorMessage = "OldPasswordRequired")]
    [DataType(DataType.Password)]
    [CheckOldPassword(ErrorMessage = "OldPasswordWrong")]
    public string OldPassword { get; set; }
}

"OldPasswordRequired"的本地化工作正常.但是,我的自定义属性的本地化不起作用,并始终返回"OldPasswordWrong"消息.这是代码:

public class CheckOldPasswordAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object classInstance, ValidationContext validationContext)
    {                   
        if (oldPasswordSaved == oldPasswordTyped) //simplified
        {
            return ValidationResult.Success;
        }
        else
        {
            string errorMessage = FormatErrorMessage(ErrorMessageString);
            return new ValidationResult(errorMessage);
        }
    }

}

ErrorMessageString始终为"OldPasswordWrong",FormatErrorMessage始终返回"OldPasswordWrong".我究竟做错了什么？我正在使用新的asp.net核心数据注释本地化,所以我没有使用ErrorMessageResourceName和ErrorMessageResourceType属性(我没有任何ViewModel.Designer.cs).

Answer 1

实现适配器以进行本地化:

public class RequiredIfAttributeAdapter : AttributeAdapterBase<RequiredIfAttribute>
{
    public RequiredIfAttributeAdapter(RequiredIfAttribute attribute, IStringLocalizer stringLocalizer) : base(attribute, stringLocalizer) {}

    public override void AddValidation(ClientModelValidationContext context) {}

    public override string GetErrorMessage(ModelValidationContextBase validationContext)
    {
        return GetErrorMessage(validationContext.ModelMetadata, validationContext.ModelMetadata.GetDisplayName());
    }
}

实现适配器的提供程序:

public class CustomValidationAttributeAdapterProvider : IValidationAttributeAdapterProvider
{
    private readonly IValidationAttributeAdapterProvider _baseProvider = new ValidationAttributeAdapterProvider();

    public IAttributeAdapter GetAttributeAdapter(ValidationAttribute attribute, IStringLocalizer stringLocalizer)
    {
        if (attribute is RequiredIfAttribute)
            return new RequiredIfAttributeAdapter(attribute as RequiredIfAttribute, stringLocalizer);
        else
            return _baseProvider.GetAttributeAdapter(attribute, stringLocalizer);
    }
}

在Startup.cs中注册提供程序:

services.AddSingleton<IValidationAttributeAdapterProvider, CustomValidationAttributeAdapterProvider>();

此博客的致谢:https://blogs.msdn.microsoft.com/mvpawardprogram/2017/01/03/asp-net-core-mvc/

Answer 2

Ramin 的答案是正确的答案。但是我决定走另一条路，所以很多情况下我不必编写适配器和适配器提供程序。

这个想法是将您的特定字符串本地化器包装在服务接口中，并从验证属性本身中获取它。

public class CPFAttribute: ValidationAttribute
{
    public CPFAttribute()
    {
    }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        string cpf;

        try
        {
            cpf = (string)value;
        }
        catch (Exception)
        {
            return new ValidationResult(GetErrorMessage(validationContext));
        }

        if (string.IsNullOrEmpty(cpf) || cpf.Length != 11 || !StringUtil.IsDigitsOnly(cpf))
        {
            return new ValidationResult(GetErrorMessage(validationContext));
        }

        return ValidationResult.Success;
    }

    private string GetErrorMessage(ValidationContext validationContext)
    {
        if (string.IsNullOrEmpty(ErrorMessage))
        {
            return "Invalid CPF";
        }

        ErrorMessageTranslationService errorTranslation = validationContext.GetService(typeof(ErrorMessageTranslationService)) as ErrorMessageTranslationService;
        return errorTranslation.GetLocalizedError(ErrorMessage);
    }
}

然后可以将服务创建为：

public class ErrorMessageTranslationService
{
    private readonly IStringLocalizer<SharedResource> _sharedLocalizer;
    public ErrorMessageTranslationService(IStringLocalizer<SharedResource> sharedLocalizer)
    {
        _sharedLocalizer = sharedLocalizer;
    }

    public string GetLocalizedError(string errorKey)
    {
        return _sharedLocalizer[errorKey];
    }
}

该服务可以在 Startup 类中注册为单例。

services.AddSingleton<ErrorMessageTranslationService>();

如果需要将这些验证属性分解到另一个程序集，只需为此翻译服务创建一个接口，您创建的所有验证属性都可以引用该接口。