c# - UniqueNationalId.IsValid(对象值，ValidationContext validateContext)

我写了一个自定义属性：

public class UniqueNationalId : ValidationAttribute
 {
  private readonly UserService _userService;

public UniqueNationalId()
{
    _userService = new UserService();
}

protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
    if (_userService.IsNationalIdExist(value.ToString()))
        return new ValidationResult("National code is available in the system");
    return null;
}

我使用IsNationalIdExist方法：

    public bool IsNationalIdExist(string nationalId)
    {
        var validateName = _user.FirstOrDefault
                            (x => x.UserId == nationalId);
        if (validateName != null)
        {
            return true;
        }
        else
        {
            return false;
        }
       // return false;
    }

类模型：

[IsValidNationalId]
    [UniqueNationalId]
    public string NationalId { get; set; }

错误给出以下内容

在UniqueNationalId.IsValid（对象值，ValidationContextvalidationContext）

我应该进行哪些更改？

最佳答案

如果验证成功，则应返回ValidationResult.Success，否则返回错误消息，即

protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
    if (_userService.IsNationalIdExist(value.ToString()))
        return ValidationResult.Success;
    else
        return new ValidationResult("National code is not available in the system");
}