c# - 如何将参数传递给 ValidationAttribute？

Question

我有一个自定义的 ValidationAttribute，它检查另一个用户是否已经存在。为此，它需要访问我的数据访问层，一个由 Unity 注入(inject)我的 Controller 的实例

我如何将这个(或与此相关的任何东西)作为参数传递到我的自定义验证器中？

这可能吗？即我在创建 Dal 的地方，这应该是一个参数

public class EmailIsUnique : ValidationAttribute
    {
        private string _errorMessage = "An account with this {0} already exists";

        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            DataAccessHelper Dal = new DataAccessHelper(SharedResolver.AppSettingsHelper().DbConnectionString); //todo, this is way too slow
            bool isValid = true;
            if(value == null) {
                isValid = false;
                _errorMessage = "{0} Cannot be empty";
            } else {
                string email = value.ToString();
                if (Dal.User.FindByEmail(email) != null)
                {
                    isValid = false;
                }
            }

            if (isValid)
                return ValidationResult.Success;
            else
                return new ValidationResult(String.Format(_errorMessage, validationContext.DisplayName));
        }
    }

Answer 1

我不太确定您是否能够将运行时参数传递到您的属性中。

你可以使用 DependencyResolver.Current.GetService<DataAccessHelper>()解决你的 dal(假设你已经注册了 DataAccessHelper)

您可能更可能将 DataAccessHelper 注册为 IDataAccessHelper 或其他什么？在这种情况下你会调用GetService<IDataAccessHelper>

public class EmailIsUnique : ValidationAttribute
{
    private string _errorMessage = "An account with this {0} already exists";

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        IDataAccessHelper Dal = DependencyResolver.Current.GetService<IDataAccessHelper>(); // too slow
        bool isValid = true;
        if(value == null) {
            isValid = false;
            _errorMessage = "{0} Cannot be empty";
        } else {
            string email = value.ToString();
            if (Dal.User.FindByEmail(email) != null)
            {
                isValid = false;
            }
        }

        if (isValid)
            return ValidationResult.Success;
        else
            return new ValidationResult(String.Format(_errorMessage, validationContext.DisplayName));
    }
}

或

public class EmailIsUnique : ValidationAttribute
{
    [Dependency]
    public IDataAccessHelper DataAccess {get;set;}

    private string _errorMessage = "An account with this {0} already exists";

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

        bool isValid = true;
        if(value == null) 
        {
            isValid = false;
            _errorMessage = "{0} Cannot be empty";
        } 
       else 
       {
            string email = value.ToString();
            if (DataAccess.User.FindByEmail(email) != null)
            {
                isValid = false;
            }
        }

        if (isValid)
            return ValidationResult.Success;
        else
            return new ValidationResult(String.Format(_errorMessage, validationContext.DisplayName));
    }
}