允许使用PhoneAttribute或UrlAttribute标记的字段使用空字符串 [英] Allow empty strings for fields marked with PhoneAttribute or UrlAttribute

问题描述

我使用CodeFirst Entitty框架5.我有一个表示用户的类。

I'm using CodeFirst Entitty framework 5. I have a class representing a user.

public class User
{
    [Key]
    public int UserId { get; set; }

    [Url]
    [DataType(DataType.Url)]
    [Required(AllowEmptyStrings= true)]
    public string WebSite { get; set; }

    [Phone]
    [DataType(DataType.PhoneNumber)]
    [Required(AllowEmptyStrings = true)]
    public string Phone { get; set; }

    [Phone]
    [DataType(DataType.PhoneNumber)]
    [Required(AllowEmptyStrings = true)]
    public string Fax { get; set; }
}

我喜欢电话的验证机制和 Url 属性很多，但不幸的是验证失败，当标记这些属性的字段是我实际想要允许的空字符串。 [必需（AllowEmptyStrings = true）] 似乎不适用于电话或网址属性。同样的情况似乎也适用于某些其他DataAnnotations属性，如 EmailAddress 。

I like the validation mechanics for Phone and Url attributes a lot, but unfortunately validation fails when fields marked with these attributes are empty strings which I actually want to allow. [Required(AllowEmptyStrings = true)] doesn't seem to work with Phone or Url attributes. The same seems to apply to some other DataAnnotations attributes like EmailAddress.

有没有办法让空字符串标有这样的属性的字段？

Is there a way to allow empty strings for fields marked with such attributes?

推荐答案

验证属性如 [Phone] 和 [EmailAddress] 将检查任何非空字符串值。因为 string 类型本身是可空的，所以传递给ModelBinder的空字符串将被读取为 null ，通过验证检查

Validation attributes like [Phone] and [EmailAddress] will check any non-null string values. Because the string type is inherently nullable, empty strings passed to the ModelBinder are read as null, which passes the validation check.

当您添加 [必需] 属性时，该字符串将变得有效地不可为空。 （如果使用代码优先，EF将脚本不可空数据库列。）ModelBinder现在将解释一个空值为 String.Empty - 这将导致属性验证检查失败

When you add the [Required] attribute, the string becomes effectively non-nullable. (If using Code First, EF will script a non-nullable database column.) The ModelBinder will now interpret a blank value as String.Empty - which will fail the attribute validation check.

所以没有办法允许具有验证属性的空字符串，但您可以允许 null 字符串。所有你需要做的是删除 [必需] 属性。空值将为 null ，非空白值将被验证。

So there is no way to allow empty strings with validation attributes, but you can allow null strings. All you need to do is remove the [Required] attribute. Blank values will be null and non-blank values will be validated.

在我的情况下，我正在导入记录从CSV文件，并有这个问题，因为我正在跳过正常的ModelBinder。如果您正在做这种不寻常的事情，请确保在保存到数据模型之前包含手动检查：

In my case, I am importing records from a CSV file, and had this problem because I was skipping the normal ModelBinder. If you are doing something unusual like this, be sure to include a manual check before saving to your data model:

Email = (record.Email == String.Empty) ? null : record.Email

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