C# vb.net nullable inotifypropertychanged

INotifyPropertyChanged 的可空类型和属性

发布于 2024-08-18 07:43:43 字数 1555 浏览 7 评论 0原文

设置可为 null 类型的值并实现 iNotifyPropertyChanged 似乎有点矫枉过正。有更好的方法吗？

        Private _WorkPhone As Long?
    Public Property [WorkPhone]() As Long?
        Get
            Return _WorkPhone
        End Get
        Set(ByVal value As Long?)
            If value.HasValue = False Then
                If _WorkPhone.HasValue = True Then
                    MyBase.RaisePropertyChanging("WorkPhone")
                    _WorkPhone = Nothing
                    MyBase.MarkDirty()
                    MyBase.RaisePropertyChanged("WorkPhone")
                End If
            Else
                If _WorkPhone.HasValue Then
                    If _WorkPhone.Value <> value.Value Then
                        MyBase.RaisePropertyChanging("WorkPhone")
                        _WorkPhone = value
                        MyBase.MarkDirty()
                        MyBase.RaisePropertyChanged("WorkPhone")
                    End If
                Else
                    MyBase.RaisePropertyChanging("WorkPhone")
                    _WorkPhone = value
                    MyBase.MarkDirty()
                End If
                MyBase.RaisePropertyChanged("WorkPhone")
            End If
        End Set
    End Property

我尝试使用简单的代码，但 MyBase.RaisePropertyChanging("WorkPhone") 上的断点从未被命中，并且该值也从未改变。

    If _WorkPhone <> value Then
    MyBase.RaisePropertyChanging("WorkPhone")
    _WorkPhone = value
    MyBase.MarkDirty()
    MyBase.RaisePropertyChanged("WorkPhone")
End If

原文

It seems like overkill to set the value of a nullable type and implement iNotifyPropertyChanged. Is there a better way of doing this?

        Private _WorkPhone As Long?
    Public Property [WorkPhone]() As Long?
        Get
            Return _WorkPhone
        End Get
        Set(ByVal value As Long?)
            If value.HasValue = False Then
                If _WorkPhone.HasValue = True Then
                    MyBase.RaisePropertyChanging("WorkPhone")
                    _WorkPhone = Nothing
                    MyBase.MarkDirty()
                    MyBase.RaisePropertyChanged("WorkPhone")
                End If
            Else
                If _WorkPhone.HasValue Then
                    If _WorkPhone.Value <> value.Value Then
                        MyBase.RaisePropertyChanging("WorkPhone")
                        _WorkPhone = value
                        MyBase.MarkDirty()
                        MyBase.RaisePropertyChanged("WorkPhone")
                    End If
                Else
                    MyBase.RaisePropertyChanging("WorkPhone")
                    _WorkPhone = value
                    MyBase.MarkDirty()
                End If
                MyBase.RaisePropertyChanged("WorkPhone")
            End If
        End Set
    End Property

I tried using simple code, but my breakpoint on MyBase.RaisePropertyChanging("WorkPhone") is never hit, and the value never changes.

    If _WorkPhone <> value Then
    MyBase.RaisePropertyChanging("WorkPhone")
    _WorkPhone = value
    MyBase.MarkDirty()
    MyBase.RaisePropertyChanged("WorkPhone")
End If

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黯然#的苍凉 2024-08-25 07:43:43

不需要所有复杂的逻辑。如果 x 和 y 都是具有相同底层类型的可空值，则 x 等于 y 当且仅当

x.HasValue 为 true
y.HasValue 为 true
x.Value 等于 y.Value

或

x.HasValue 为 false
y.HasValue 为 false

在这两种情况下在某些情况下，我们想要发出属性更改通知，因此对不相等性的简单测试就足够了。因此：

Private _WorkPhone As Long?
    Public Property [WorkPhone]() As Long?
        Get
            Return _WorkPhone
        End Get
        Set(ByVal value As Long?)
            If Not _workPhone.Equals(value)
                MyBase.RaisePropertyChanging("WorkPhone")
                _WorkPhone = value
                MyBase.MarkDirty()
                MyBase.RaisePropertyChanged("WorkPhone")
            EndIf
        End Set
    End Property

请注意，我们需要使用 Not Nullable(Of T).Equals 而不是 <>，因为后者的计算结果为 Nothing 如果如果其操作数为 Nothing，则为 1。

There is no need for all the complicated logic. If x and y are both nullables with the same underlying type then x equals y if and only if

x.HasValue is true
y.HasValue is true
x.Value equals y.Value

x.HasValue is false
y.HasValue is false

In neither of these cases would we want to raise a property changed notification and thus a simple test for non-equality will suffice. Thus:

Private _WorkPhone As Long?
    Public Property [WorkPhone]() As Long?
        Get
            Return _WorkPhone
        End Get
        Set(ByVal value As Long?)
            If Not _workPhone.Equals(value)
                MyBase.RaisePropertyChanging("WorkPhone")
                _WorkPhone = value
                MyBase.MarkDirty()
                MyBase.RaisePropertyChanged("WorkPhone")
            EndIf
        End Set
    End Property

Note that we ned to use Not Nullable(Of T).Equals instead of <> as the latter evaluates to Nothing if one if its operands is Nothing.

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