滑块上的WPF绑定不会在最大更改时更新 combobox1.SelectedItem绑定到SelectedItemProperty 设置SelectedItemProperty时，将计算MaxValueProperty

MaxValueProperty

绑定到

slider1。最大值

slider1.Value

绑定到

SliderValueProperty

除了当

combobox1.SelectedItem

发生更改，并且计算了

MaxValueProperty

，结果小于

SliderValueProperty

时，这些都可以正常工作

他认为：

• slider1.Maximum

  已更新，因为

  MaxValueProperty

  已更改

• slider1.Value

  设置为

  slider1.max

  ，作为最大值更改为小于该值时滑块的默认行为

但是，发生这种情况时，

SliderValueProperty

不会更新为新的

slider1.Value

<Slider Name="slider1" Maximum="{Binding Path=MaxValueProperty, Mode=TwoWay}" Value="{Binding Path=SliderValueProperty, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />

我知道slider1.Value正在更改，因为我有一个绑定到它的标签，并且标签会更改

<Label Content="{Binding ElementName=slider, Path=Value, Converter={StaticResource NumberToStringConverter}}" />

---

如何确保绑定已更新？

与其依赖滑块的默认行为和双向

绑定，不如在
SelectedItemProperty
setter中计算新的最大值后，首先使用新的最大值在“SliderValueProperty”上，然后在“MaxValueProperty”。在私人支持字段上进行计算，而不是在公共属性上

这将导致系统首先调整滑块的值，然后调整maxvalue，并且它将为您移动滑块位置

将slider1的
最大值
上的绑定模式也设置为
单向
；我认为这样就可以了

对于这样的viewmodel，如下所示：

Class viewmodel
    Implements INotifyPropertyChanged
Private _selectedItemProperty As ComboBoxItem
Public Property SelectedItemProperty As ComboBoxItem

    Get
        Return _selectedItemProperty
    End Get
    Set(value As ComboBoxItem)
        MaxValueProperty = value.Content
        If _sliderValueProperty > _maxValueProperty Then _sliderValueProperty = _maxValueProperty
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("MaxValueProperty"))
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("SliderValueProperty"))
    End Set
End Property
Private _maxValueProperty, _sliderValueProperty as Single
Public Property MaxValueProperty As Single ' with setter that will raise PropertyChanged and use the backing field

'...

Public Property SliderValueProperty As Single ' with a setter that will raise PropertyChanged and use the backing field

'...

End Class

    <Grid>
    <ComboBox Height="23" HorizontalAlignment="Left" Margin="40,38,0,0" Name="ComboBox1" VerticalAlignment="Top" Width="120" SelectedItem="{Binding SelectedItemProperty}">
        <ComboBoxItem Content="50" />
        <ComboBoxItem Content="30" />
        <ComboBoxItem Content="10" />
    </ComboBox>
    <Slider Name="slider1" Height="23" HorizontalAlignment="Left" Margin="87,135,0,0"  VerticalAlignment="Top" Width="100" Value="{Binding SliderValueProperty}" Minimum="1" Maximum="{Binding MaxValueProperty}" />
    <Label Content="{Binding ElementName=slider1, Path=Value}" Margin="40,174,293,96" />

</Grid>

XAML看起来有点像这样：

Class viewmodel
    Implements INotifyPropertyChanged
Private _selectedItemProperty As ComboBoxItem
Public Property SelectedItemProperty As ComboBoxItem

    Get
        Return _selectedItemProperty
    End Get
    Set(value As ComboBoxItem)
        MaxValueProperty = value.Content
        If _sliderValueProperty > _maxValueProperty Then _sliderValueProperty = _maxValueProperty
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("MaxValueProperty"))
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("SliderValueProperty"))
    End Set
End Property
Private _maxValueProperty, _sliderValueProperty as Single
Public Property MaxValueProperty As Single ' with setter that will raise PropertyChanged and use the backing field

'...

Public Property SliderValueProperty As Single ' with a setter that will raise PropertyChanged and use the backing field

'...

End Class

    <Grid>
    <ComboBox Height="23" HorizontalAlignment="Left" Margin="40,38,0,0" Name="ComboBox1" VerticalAlignment="Top" Width="120" SelectedItem="{Binding SelectedItemProperty}">
        <ComboBoxItem Content="50" />
        <ComboBoxItem Content="30" />
        <ComboBoxItem Content="10" />
    </ComboBox>
    <Slider Name="slider1" Height="23" HorizontalAlignment="Left" Margin="87,135,0,0"  VerticalAlignment="Top" Width="100" Value="{Binding SliderValueProperty}" Minimum="1" Maximum="{Binding MaxValueProperty}" />
    <Label Content="{Binding ElementName=slider1, Path=Value}" Margin="40,174,293,96" />

</Grid>


在您回答之前不久，我对您的if语句做了类似的处理，但是是在属性上，分配SliderValueProperty会引发propertychanged事件，解决了我的问题。但有一个问题-为什么要在私有支持字段上进行计算，然后手动引发property changed事件？根据您的问题描述，请回答当MVVM使用时，这似乎是最明确、最直接的方法。您有一个属性设置器，它可以更改其他属性的条件，虽然您可以按照您选择的方式毫无问题地执行，但我对您的程序一无所知。我通常选择在需要更改时明确提出PropertyChanged是的，这只是
if（SliderValueProperty>MaxValueProperty）{SliderValueProperty=MaxValueProperty；}
和
if（SliderValueProperty>\MaxValueProperty）{SliderValueProperty=\MaxValueProperty；RaisePropertyChanged（SliderValueProperty）；}