使用 INotifyPropertyChanged 进行绑定

Question

在我的项目中，每当有新的投标价格出现时，我想更改 Datagrid 单元格的背景。 我设置它使用

public class Notifier : INotifyPropertyChanged
{
public bool BidUp
{
    get { return _bidUp; }
    set
    {
        _bidUp = value;
        OnPropertyChanged("BidUp");
    }
}
public double Bid
{
    get { return _bid; }
    set
    {
        BidUp = (value > this.Bid);
        _bid = value;
        OnPropertyChanged("Bid");
    }
}

public event PropertyChangedEventHandler PropertyChanged;

protected void OnPropertyChanged(string propertyName)
{
    var handler = PropertyChanged;
    if (handler != null)
        handler(this, new PropertyChangedEventArgs(propertyName));
}
}

还有我的 DataGridCell 的 xaml 代码：

<DataTemplate>
<Border x:Name="BidBoder" Background="AliceBlue" BorderThickness="0">
    <TextBlock Text="{Binding Bid}" x:Name="BidTextBlock" HorizontalAlignment="Right"></TextBlock>
</Border>
<DataTemplate.Triggers>
    <DataTrigger Binding="{Binding BidUp}" Value="True">
        <DataTrigger.EnterActions>
            <StopStoryboard BeginStoryboardName="bidUpStoryboard"/>
            <StopStoryboard BeginStoryboardName="bidDownStoryboard"/>
            <BeginStoryboard Name="bidUpStoryboard">
                <Storyboard BeginTime="00:00:00">
                    <ColorAnimation 
                        BeginTime="00:00:00"
                        Duration="0:0:0.1" 
                        To="LimeGreen" 
                        AutoReverse="True"
                        Storyboard.TargetName="BidBoder" 
                        Storyboard.TargetProperty="(Border.Background).(SolidColorBrush.Color)">
                    </ColorAnimation>
                </Storyboard>
            </BeginStoryboard>
        </DataTrigger.EnterActions>
    </DataTrigger>
    <DataTrigger Binding="{Binding BidUp}" Value="False">
        <DataTrigger.EnterActions>
            <StopStoryboard BeginStoryboardName="bidUpStoryboard"/>
            <StopStoryboard BeginStoryboardName="bidDownStoryboard"/>
            <BeginStoryboard Name="bidDownStoryboard">
                <Storyboard BeginTime="00:00:00">
                    <ColorAnimation 
                        BeginTime="00:00:00"
                        Duration="0:0:0.1" 
                        To="Red" 
                        AutoReverse="True"
                        Storyboard.TargetName="BidBoder" 
                        Storyboard.TargetProperty="(Border.Background).(SolidColorBrush.Color)">
                    </ColorAnimation>
                </Storyboard>
            </BeginStoryboard>
        </DataTrigger.EnterActions>
    </DataTrigger>
</DataTemplate.Triggers>

现在发生的情况是，如果价格上涨后又上涨，BidUp = true--->true propertyChanged 不会触发。即使_bidUp = value 没有改变，有没有办法触发改变？
我想问一下如果Property A = somevalue 被调用，为什么OnPropertyChanged 不被调用，如果相同的值适用？

Answer 1

您有两种方法可以在同一个 setter 中触发多个属性的更新：

public double Bid
{
    get { return _bid; }
    set
    {
        BidUp = (value > this.Bid);
        _bid = value;
        OnPropertyChanged("Bid");
        OnPropertyChanged("BidUp"); // notify both properties in the same setter
    }
}

还是

public double Bid
{
    get { return _bid; }
    set
    {
        BidUp = (value > this.Bid);
        _bid = value;
        OnPropertyChanged(null); // notify change of EVERY property - good if few properties in ViewModel
    }
}

Answer 2

考虑绑定到代表实际值的属性，然后使用多重绑定（即 currentValue 和 previousValue）来更新您的 UI。