DataTrigger 在 RadioButton IsChecked 时更新 DatePicker答案

【问题标题】：DataTrigger to Update a DatePicker when a RadioButton IsCheckedDataTrigger 在 RadioButton IsChecked 时更新 DatePicker
【发布时间】：2019-12-16 15:15:35
【问题描述】：

我只是想根据单选按钮的 IsChecked 在 DatePicker 中设置 SelectedDate。当单选按钮 IsChecked 为 true 时，应在 DatePicker 中输入今天的日期。如果 IsChecked 为 false，则 DatePicker 应为空。我尝试了数据触发器的各种版本，但都没有产生任何好处。无论单选按钮是什么，DatePicker 中都不会填充任何内容。为了让它正常工作，我缺少什么？

<DatePicker Grid.Row="19" Grid.Column="1" Width="120" SelectedDate="{Binding SelectedApplication.DateHireDeclineSent}"
            Visibility="{Binding IsChecked, ElementName=HireDeclinedYes, Converter={StaticResource BooleanToVisibilityConverter}}" >
    <DatePicker.Style>
        <Style TargetType="DatePicker">                                    
            <Style.Triggers>
                <DataTrigger Binding="{Binding ElementName=HireDeclinedYes, Path=IsChecked, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" Value="True">
                    <Setter Property="SelectedDate" Value="{x:Static sys:DateTime.Now}"/>
                </DataTrigger>
                <DataTrigger Binding="{Binding ElementName=HireDeclinedYes, Path=IsChecked}" Value="False">
                    <Setter Property="SelectedDate" Value="{x:Null}"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </DatePicker.Style>
</DatePicker>

<StackPanel Grid.Row="16" Grid.Column="4" Orientation="Horizontal"
            Visibility="{Binding IsChecked,ElementName=NoHireAdd, Converter={StaticResource BooleanToVisibilityConverter}}">
    <RadioButton x:Name="HireDeclinedYes" Content="Yes" IsChecked="{Binding SelectedApplication.HireDeclined}" />
    <RadioButton x:Name="HireDeclinedNo" Margin="5,0,0,0" Content="No" IsChecked="{Binding SelectedApplication.HireDeclined, Converter={StaticResource BoolInverterConverter}}" />
</StackPanel>

【问题讨论】：

标签： c# wpf datatrigger

【解决方案1】：

如果您删除 SelectedDate="{Binding SelectedApplication.DateHireDeclineSent}" 并使用 setter 设置默认值，它应该可以工作：

<DatePicker Grid.Row="19" Grid.Column="1" Width="120"
            Visibility="{Binding IsChecked, ElementName=HireDeclinedYes, Converter={StaticResource BooleanToVisibilityConverter}}" >
    <DatePicker.Style>
        <Style TargetType="DatePicker">
            <Setter Property="SelectedDate" Value="{Binding SelectedApplication.DateHireDeclineSent}" />
            <Style.Triggers>
                <DataTrigger Binding="{Binding ElementName=HireDeclinedYes, Path=IsChecked, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" Value="True">
                    <Setter Property="SelectedDate" Value="{x:Static sys:DateTime.Now}"/>
                </DataTrigger>
                <DataTrigger Binding="{Binding ElementName=HireDeclinedYes, Path=IsChecked}" Value="False">
                    <Setter Property="SelectedDate" Value="{x:Null}"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </DatePicker.Style>
</DatePicker>

本地值优先于样式设置器：https://docs.microsoft.com/en-us/dotnet/framework/wpf/advanced/dependency-property-value-precedence

【讨论】：

太棒了！感谢@mm8 成功了！我也学到了一些东西。

【解决方案2】：

由于 DatePicker SelectedDate 绑定到 SelectedApplication.DateHireDeclineSent 并且单选按钮 IsChecked 属性绑定到 SelectedApplication.HireDeclined ，您可以在 setter 的 SelectedApplication.HireDeclined 是否也更改 SelectedApplication.DateHireDeclineSent 属性并引发属性更改事件？

这将更改 DatePicker 绑定的属性，并且属性更改事件将通知视图有关更改，从而更改 DatePicker SelectedDate。

就像这样：

private bool _hireDeclined;
public bool HireDeclined
{
    get => _hireDeclined;
    set 
    {
        _hireDeclined = value;
        NotifyPropertyChanged("HireDeclined");
        if (//some condition)
            DateHireDeclineSent = DateTime.Now;
    }
}

private DateTime _dateHireDeclineSent;
public DateTime DateHireDeclineSent
{
    get => _dateHireDeclineSent;
    set
    {
        _dateHireDeclineSent = value;
        NotifyPropertyChanged("DateHireDeclineSent");
    }
}

【讨论】：