Question

繁殖：

Imports System.ComponentModel
Imports System.ComponentModel.DataAnnotations
Module Module1

  Sub Main()
    Dim type = GetType(Contact)
    TypeDescriptor.AddProviderTransparent(
      New AssociatedMetadataTypeTypeDescriptionProvider(type), type)


    Dim contact As New Contact
    Dim context As New ValidationContext(contact, Nothing, Nothing)
    Dim errors As New List(Of ValidationResult)
    Dim result = Validator.TryValidateObject(contact, context, errors, True)
  End Sub
End Module

<CustomValidation(GetType(Contact.ContactMd), "*********************")>
<MetadataType(GetType(Contact.ContactMd))>
Public Class Contact

  Public Property Email As String
  Public Property EmailRepeat As String

  Public Class ContactMd

    '<Required()>
    Public Property Email
    '<Required()>
    Public Property EmailRepeat

    Public Shared Function ValidateEmails(ByVal contact As Contact) _
        As ValidationResult
      Return If(contact.Email = contact.EmailRepeat,
                ValidationResult.Success,
                New ValidationResult("Fail!"))
    End Function
  End Class
End Class

以上代码将引发异常：
The CustomValidationAttribute method '*********************' does not exist in type 'ContactMd' or is not public and static.

这个例外是合理的，这表明事情正在发挥作用。一旦我取消了Md类中属性的Required属性，就不会抛出异常，这意味着验证系统不会对属性类型属性和类级属性进行验证。

任何解决方法？

Answer 1

答案是，验证系统首先验证属性验证属性（在这种情况下为Required属性），并且只有在对象传递属性属性时才会进入CustomValidationAttribute。 / p>

所以根据上面的复制，更改行

Dim contact As New Contact

等等（允许enitity传递属性验证）：

Dim contact As New Contact With { .Email = "*", .EmailRepeat = "*" }

将抛出预期的异常。

Answer 2

CustomValidationAttribute指定的方法的签名必须是：

VB：

Public Shared Function OnValidate(
    entity As Contact, context As ValidationContext) As ValidationResult

C＃：

public static ValidationResult OnValidate(Contact entity, ValidationContext context)

如果验证正常，则应返回ValidationResult.Success。

当其他属性应用于类时，CustomValidationAttribute不起作用

2 个答案: