Question

我的代码类似于以下内容：

Imports System.ComponentModel.DataAnnotations
Class Person
    Dim _ssn As String = ""
    Public Overridable Property SSN(format As Boolean) As String
    Get
        If format Then
            ' Return formatted SSN
        Else : Return _ssn
        End If
    End Get
    Set(value As String)
        _ssn = value
    End Set
    End Property
End Class

Class Employee
    Inherits Person

    <Required()>
    Public Overrides Property SSN(format As Boolean) As String
    Get
        Return MyBase.SSN(format)
    End Get
    Set(value As String)
        MyBase.SSN(format) = value
    End Set
End Property
End Class

当我在Employee类上使用Validator.ValidateObject（）时，即使SSN属性为Nothing，它也会正常验证。

为什么所需属性不起作用？

由于

Answer 1

我怀疑验证不适用于索引/参数化属性，因为我不知道验证程序如何计算出format参数传入的内容。作为一种变通方法，您可以创建一个非索引属性来放置Required属性。

Class Employee
    Inherits Person

    <Required()>
    Public Overloads Property SSN As String
        Get
            Return Me.SSN(False)
        End Get
        Set(value As String)
            Me.SSN(False) = value
        End Set
    End Property

    Public Overrides Property SSN(format As Boolean) As String
        Get
            Return MyBase.SSN(format)
        End Get
        Set(value As String)
            MyBase.SSN(format) = value
        End Set
    End Property

End Class

说实话，我可能会将设计更改为具有两个属性 - 读/写SSN属性和只读FormattedSSN属性，这对我来说似乎更干净（但可能是＆＃39;只是我！）。

Answer 2

看起来参数化属性不会采用必需的属性。作为一种解决方法，我使用重载来解决这个问题。

Imports System.ComponentModel.DataAnnotations

Class Person

    Dim _ssn As String
    Public Property SSN() As String
        Get
            Return _ssn
        End Get
        Set(ByVal value As String)
            _ssn = JustNumbers(value)
        End Set
    End Property

    Public Property SSN(format As String) As String
        Get
            Try
                Return CInt(Me.SSN).ToString(format)
            Catch ex As InvalidCastException : Return Me.SSN
            End Try
        End Get
        Set(value As String)
            SSN = value
        End Set
    End Property

    Function IsValid() As Boolean
        Return Validator.TryValidateObject(Me, New ValidationContext(Me), Nothing)
    End Function
End Class

Class Employee
    Inherits Person

    <Required()>
    Public Overloads Property SSN() As String
        Get
            Return MyBase.SSN
        End Get
        Set(value As String)
            MyBase.SSN = value
        End Set
    End Property
End Class

使用DataAnnotations需要继承的属性

2 个答案: