Question

我有一个问题。

我正在使用2扩展工具包DateTimePicker，并且mu目标是这样的情况：如果你改变时间，一个开始选择器结束选择器将在5分钟后随时间更新，反之亦然如果我在结束开始时改变值将返回5分钟。

我尝试使用ValueChanged属性，但没有运气，最终导致例外情况：

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"/>

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？

Answer 1

看看interraction triggers。使用它们，您可以使用您的ui中的特定事件在您的虚拟机中调用命令

Answer 2

我做了一个基于Interaction.Behaviors xaml的解决方案看起来像：

    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);
    }
}

PropertyChangedCommand的逻辑：

public class PropertyChangeBehavior：Behavior { public static readonly DependencyProperty PropertyChangedCommandProperty = DependencyProperty.Register（＆＃34; PropertyChangedCommand＆＃34;，typeof（ICommand）， typeof（PropertyChangeBehavior），new PropertyMetadata（null，ApplyChanged））;

struct

命令保持不变，并且有效。

WPF中的WPF扩展工具包DateTimePicker更改值事件

2 个答案: