如何将用户控件属性绑定到其他属性？

Question

我有以下用户控件：

Xaml:

<UserControl x:Class="ScreenRecorder.TimePicker"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" Height="27" Width="176">
<Grid>
    <StackPanel Orientation="Horizontal">
        <TextBox  Width="150" Height="25" Text="{Binding Time}" HorizontalAlignment="Left" VerticalAlignment="Top"/>
        <StackPanel Orientation="Vertical">
            <Button Width="25" Height="12.5" HorizontalAlignment="Left" VerticalAlignment="Top" Click="btnKeyUp_Clicked">
                <Image Source="up.png" Height="10" Width="10" VerticalAlignment="Top"/>
            </Button>
            <Button Width="25" Height="12.5" HorizontalAlignment="Left" VerticalAlignment="Top" Click="btnKeyDown_Clicked">
                <Image Source="down.png" Height="10" Width="10" VerticalAlignment="Top"/>
            </Button>
        </StackPanel>
    </StackPanel>
</Grid>

代码：

 public partial class TimePicker : UserControl, INotifyPropertyChanged
{
    public TimePicker()
    {
        InitializeComponent();
        this.DataContext = this;
        //Time = m_time;
    }

    public static DependencyProperty TimeProperty = DependencyProperty.Register(
        "Time", typeof(string), typeof(TimePicker));

    //private string m_time = DateTime.Now.ToString();
    public string Time
    {
        get { return (string)GetValue(TimeProperty); }
        set
        {
            SetValue(TimeProperty, value);
            NotifyPropertyChanged("Time");
        }
    }

    private void btnKeyUp_Clicked(object sender, RoutedEventArgs e)
    {
        DateTime curTime = Convert.ToDateTime(Time);
        curTime += new TimeSpan(0, 0, 1);
        Time = curTime.ToString();
    }

    private void btnKeyDown_Clicked(object sender, RoutedEventArgs e)
    {
        DateTime curTime = Convert.ToDateTime(Time);
        curTime -= new TimeSpan(0, 0, 1);
        Time = curTime.ToString();
    }

    #region INotifyPropertyChanged
    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged(String propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    #endregion
}

我还有另一个使用此用户控件的用户控件，如下所示：

        <StackPanel>
            <Label Content="Begin Record Time" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="5"/>
            <local:TimePicker Time="{Binding StartRecordTime}"/>
        </StackPanel>

StartRecordTime 看起来像这样：

public string StartRecordTime
    {
        get { return m_startRecord; }
        set
        {
            m_startRecord = value;
            NotifyPropertyChanged("StartRecordTime");
        }
    }

我想根据时间属性更改 StartRecordTime，反之亦然，但只有时间属性正在更改。

谢谢。

Answer 1

试试这个：

<local:TimePicker Time="{Binding Path=StartRecordTime, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"/>

Answer 2

您的绑定将不起作用，因为您已将 TimePicker 的 DataContext 设置为 TimePicker 本身。您会注意到输出中存在绑定错误 window:

BindingExpression path error: 'StartRecordTime' property not found on 'object' ''TimePicker' (Name='')'. BindingExpression:Path=StartRecordTime; DataItem='TimePicker' (Name=''); target element is 'TimePicker' (Name=''); target property is 'Time' (type 'String')

我建议您从 TimePicker 构造函数中删除 DataContext = this 并将网格的 DataContext 设置为 TimePicker 以获得更多 'sane' 经验按元素名称。向 UserControl 元素添加名称属性：

<UserControl x:Name="Root" ...

并设置Grid的DataContext:

<Grid DataContext="{Binding ElementName=Root}">

这将被所有子元素继承。您还需要明确地将绑定更改为 TwoWay：

<local:TimePicker Time="{Binding Path=StartRecordTime, Mode=TwoWay}" />

或者在 DependencyProperty 注册中将其设置为默认值：

public static readonly DependencyProperty TimeProperty = DependencyProperty.Register(
    "Time", typeof(string), typeof(TimePicker), 
    new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));

我还要指出 TimePicker 没有理由实施 INotifyPropertyChanged。我建议你删除这个。

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