当我尝试在 DatePicker 上设置 TargetUpdated 事件时出现 "Type must derive from DependencyObject" 错误

Question

我有一个 XAML DatePicker 是这样定义的：

<DatePicker x:Name="startDateDatePicker" Validation.ErrorTemplate="{StaticResource validationTemplate}"
SelectedDateChanged="window_DatePicker_SelectedDateChanged" Validation.Error="ValidationError">
    <DatePicker.SelectedDate>
        <Binding Path="startDate" Mode="TwoWay" NotifyOnValidationError="True" ValidatesOnExceptions="True" UpdateSourceTrigger="PropertyChanged">
            <Binding.ValidationRules>
                <!-- A couple custom rules. //-->
            </Binding.ValidationRules>
         </Binding>
    </DatePicker.SelectedDate>
</DatePicker>

我需要在我的 DatePicker.SelectedDate 对象中的 Binding 对象的 Binding.TargetUpdated 和 Binding.SourceUpdated 事件中附加一个事件处理程序。

但是，当我这样重新定义我的标签时：

<Binding Path="startDate" Mode="TwoWay" NotifyOnValidationError="True" ValidatesOnExceptions="True" UpdateSourceTrigger="PropertyChanged" TargetUpdated="BindingTargetUpdated" SourceUpdated="BindingSourceUpdaed">

我收到错误消息：

The attached property "TargetUpdated" can only be applied to types that are derived from "DependencyObject".

和

The attached property "SourceUpdated" can only be applied to types that are derived from "DependencyObject".

我需要做什么才能绑定到这些事件？我理解错误消息，但我不知道它与 <DatePicker.SelectedDate> 项目有什么关系，因为它应该是 DependencyObject.

Answer 1

如评论中所述，您需要针对 DatePicker 而不是 Binding 设置事件。此外，针对 Binding，您需要启用两个 NotifyOnTargetUpdated and NotifyOnSourceUpdated 才能引发事件。

<DatePicker ... TargetUpdated="BindingTargetUpdated" SourceUpdated="BindingSourceUpdaed">
    <DatePicker.SelectedDate>
        <Binding Path="startDate" ... NotifyOnTargetUpdated="True" NotifyOnSourceUpdated="True">
            <Binding.ValidationRules>
                <!-- A couple custom rules. //-->
            </Binding.ValidationRules>
         </Binding>
    </DatePicker.SelectedDate>
</DatePicker>

当我尝试在 DatePicker 上设置 TargetUpdated 事件时出现 "Type must derive from DependencyObject" 错误

Getting an "Type must derive from DependencyObject" error, when I try to to set a TargetUpdated event on a DatePicker

wpf

events

xaml

binding

datepicker