使用INotifyPropertyChanged进行绑定 [英] Binding using INotifyPropertyChanged

问题描述

在我的项目中，无论何时出现新的出价，我都想更改Datagrid单元格的背景. 然后使用

进行设置

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>

现在发生的事情是，如果价格先上涨又上涨，BidUp = true--->true propertyChanged不会触发.
我想问一问是否调用了Property A = somevalue，为什么要应用OnPropertyChanged呢?

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
    }
}

如果相同的值适用，为什么不调用OnPropertyChanged呢?

解决方案

您可以通过两种方式触发同一设置程序中多个属性的更新:

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
    }
}

In my project I wanna change the background of a Datagrid cell whenever a new Bid price comes in. And I set it using

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));
}
}

And my xaml code for the DataGridCell:

<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>

Now what happens is if price goes up followed by a up, BidUp = true--->true the propertyChanged does not trigger. Is there a way to trigeer a change even the _bidUp = value does not change?
And I wanna ask generally if Property A = somevalue is called, why OnPropertyChanged is not called if the same value applies?

解决方案

You have two ways of triggering the update of more than one property in the same setter:

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

or yet

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
    }
}

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