[英]WPF Extended Toolkit DateTimePicker change value event in MVVM
我有个问题。
我正在使用2 Extended Toolkit DateTimePicker,mu目标是如果您更改时间,则一个开始选择器结束选择器将在5分钟后随时间更新,反之亦然,如果我更改结束开始时的值将返回5分钟。
我尝试使用ValueChanged属性,但不幸的是,它最终出现如下异常:
输入“ System.Windows.Data.Binding”元素的值的操作触发了异常。
这些控件的Xaml很简单:
<xctk:DateTimePicker Value="{Binding StartEventDatetime}" ValueChanged="{Binding UpdateEndDatetime}"
Format="Custom" FormatString="yyyy/MM/dd HH:mm:ss" Watermark="Start Date" Foreground="White"/>
<xctk:DateTimePicker Value="{Binding EndEventDatetime}" ValueChanged="{Binding UpdateStartDatetime}"
Format="Custom" FormatString="yyyy/MM/dd HH:mm:ss" Watermark="End date" Foreground="White"/>
和命令绑定:
public ICommand UpdateStartDatetime => new Command(p => { EndEventDatetime = EndEventDatetime.AddMinutes(CurrentSamplesViewModel.MinuteTimeInterval); });
public ICommand UpdateEndDatetime => new Command(p => { StartEventDatetime = StartEventDatetime.AddMinutes(CurrentSamplesViewModel.MinuteTimeInterval); });
有没有办法创建这样的事件?
看一下触发触发器 。 与他们一起,您可以通过ui中的特定事件在vm中调用命令
Ive根据Interaction提出了一个解决方案。行为xaml如下所示:
<xctk:DateTimePicker Value="{Binding StartEventDatetime}" Format="Custom" FormatString="yyyy/MM/dd HH:mm" Watermark="Start Date" Foreground="White">
<i:Interaction.Behaviors>
<businessLogic:PropertyChangeBehavior DependencyPropertyName="Value" PropertyChangedCommand="{Binding UpdateEndDatetimeCommand}"/>
</i:Interaction.Behaviors>
</xctk:DateTimePicker>
<xctk:DateTimePicker Value="{Binding EndEventDatetime}" Format="Custom" FormatString="yyyy/MM/dd HH:mm" Watermark="End date" Foreground="White">
<i:Interaction.Behaviors>
<businessLogic:PropertyChangeBehavior DependencyPropertyName="Value" PropertyChangedCommand="{Binding UpdateStartDatetimeCommand}"/>
</i:Interaction.Behaviors>
</xctk:DateTimePicker>
PropertyChangedCommand的逻辑:
公共类PropertyChangeBehavior:行为{公共静态只读DependencyProperty PropertyChangedCommandProperty = DependencyProperty.Register(“ PropertyChangedCommand”,typeof(ICommand),typeof(PropertyChangeBehavior),new PropertyMetadata(null,ApplyChanged));
public static readonly DependencyProperty DependencyPropertyNameProperty = DependencyProperty.Register(
"DependencyPropertyName", typeof(string),
typeof(PropertyChangeBehavior), new PropertyMetadata(string.Empty, ApplyChanged));
private DependencyPropertyDescriptor descriptor;
public ICommand PropertyChangedCommand
{
get => (ICommand)GetValue(PropertyChangedCommandProperty);
set => SetValue(PropertyChangedCommandProperty, value);
}
public string DependencyPropertyName
{
get => (string)GetValue(DependencyPropertyNameProperty);
set => SetValue(DependencyPropertyNameProperty, value);
}
private static void ApplyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (d is PropertyChangeBehavior behavior)
{
behavior.Setup();
}
}
protected override void OnAttached()
{
Setup();
}
protected override void OnDetaching()
{
if (descriptor != null && AssociatedObject != null)
{
descriptor.RemoveValueChanged(AssociatedObject, OnPropertyValueChanged);
}
}
private void Setup()
{
if (descriptor != null || string.IsNullOrEmpty(DependencyPropertyName) || AssociatedObject == null)
{
return;
}
descriptor = DependencyPropertyDescriptor.FromName(DependencyPropertyName, AssociatedObject.GetType(),
AssociatedObject.GetType());
descriptor?.AddValueChanged(AssociatedObject, OnPropertyValueChanged);
}
private void OnPropertyValueChanged(object sender, EventArgs e)
{
object value = AssociatedObject.GetValue(descriptor.DependencyProperty);
if (PropertyChangedCommand == null || !PropertyChangedCommand.CanExecute(value))
{
return;
}
PropertyChangedCommand.Execute(value);
}
}
并且命令保持不变,并且可以正常工作。
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