Question

我想使用4个TextBox来设置UserControl边框的BorderThickness，但我无法让它工作。

XAML代码演示了这个问题（只需要将此代码与转换器结合使用）：

<Window 
    x:Class="BorderThicknessBindingTest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:BorderThicknessBindingTest="clr-namespace:BorderThicknessBindingTest" 
    Height="300" Width="500">
    <Window.Resources>
        <BorderThicknessBindingTest:ThicknessConverter x:Key="ThicknessConverter"/>
    </Window.Resources>

    <Grid Margin="10">
        <Border 
            x:Name="MyBorder"
            BorderBrush="Black" 
            Background="AliceBlue"
            BorderThickness="3"/>
        <TextBox 
            HorizontalAlignment="Center" VerticalAlignment="Center"
            Text="{Binding Path=BorderThickness.Left, ElementName=MyBorder, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource ThicknessConverter}}"/>
    </Grid>
</Window>

需要一个转换器来解析TextBox中的字符串输入：

public class ThicknessConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value; // don't need to do anything here
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        double d;
        Double.TryParse((string) value, out d); // Thickness.Left doesn't take a string
        return d;
    }
}

TextBox正确显示厚度的左侧部分，但编辑TextBox不会导致渲染边框左侧的方式发生变化。奇怪的是，我在ThickBox.Left的TextBox中设置的值仍然存在，因此似乎设置了值，但渲染未更新。在示例代码中，更改TextBox中的值，然后调整Window的大小，显示左侧的边框确实占用了额外的空间，但此空格为空。

有谁知道如何解决这个问题？

Answer 1

它不会动态更新屏幕上的元素，因为没有任何内容告诉元素BorderThickness属性中的字段已更改。您需要通知元素其BorderThickness已更改，您只能通过直接将依赖项属性设置为新值来执行此操作 - 例如，将其作为绑定到执行更改通知的对象的目标。

为此制作一个视图模型真是太痛苦了，但是一旦你这样做了，就完成了。

窗口：

<Window x:Class="ThicknessDemo.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:ComponentModel="clr-namespace:System.ComponentModel;assembly=System" xmlns:ThicknessDemo="clr-namespace:ThicknessDemo" Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <ThicknessDemo:ThicknessViewModel x:Key="thickness" />
    </Window.Resources>
        <DockPanel DataContext="{StaticResource thickness}">
            <Border DockPanel.Dock="Top"
                    Width="100"
                    Height="50"
                    Margin="5"
                    BorderBrush="Blue"
                    BorderThickness="{Binding Thickness}" />
            <TextBox DockPanel.Dock="Top"
                        Text="{Binding Left, Mode=TwoWay}" />
            <TextBox DockPanel.Dock="Top"
                        Text="{Binding Right, Mode=TwoWay}" />
            <TextBox DockPanel.Dock="Top"
                        Text="{Binding Top, Mode=TwoWay}" />
            <TextBox DockPanel.Dock="Top"
                        Text="{Binding Bottom, Mode=TwoWay}" />
            <TextBlock DockPanel.Dock="Top" />
        </DockPanel>
</Window>

视图模型：

public class ThicknessViewModel : INotifyPropertyChanged
{
    private void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler h = PropertyChanged;
        if (h != null)
        {
            h(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public ThicknessViewModel()
    {
        _Thickness = new Thickness(1, 1, 1, 1);
    }

    private Thickness _Thickness;

    public Thickness Thickness { get { return _Thickness; } set { _Thickness = value;} }

    public double Left
    {
        get { return _Thickness.Left; }
        set
        {
            _Thickness.Left = value;
            OnPropertyChanged("Thickness");
        }
    }

    public double Right
    {
        get { return _Thickness.Right; }
        set
        {
            _Thickness.Right = value;
            OnPropertyChanged("Thickness");
        }
    }

    public double Top
    {
        get { return _Thickness.Top; }
        set
        {
            _Thickness.Top = value;
            OnPropertyChanged("Thickness");
        }
    }

    public double Bottom
    {
        get { return _Thickness.Bottom; }
        set
        {
            _Thickness.Bottom = value;
            OnPropertyChanged("Thickness");
        }
    }
}

Answer 2

我相信这会指引你朝着正确的方向前进：在中途阅读有两种方法可以接近这种方式，一种方式使用转换器而一种方式不使用。

http://10rem.net/blog/2010/05/08/breaking-apart-the-margin-property-in-xaml-for-better-binding

Answer 3

对我来说，最简单的解决方案是只听取TextBox的TextChanged事件，并替换后面代码中的BorderThickness。

MainWindow.xaml：

<Window 
    x:Class="BorderThicknessBindingTest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:BorderThicknessBindingTest="clr-namespace:BorderThicknessBindingTest" 
    Height="300" Width="500">

    <Grid Margin="10">
        <Border 
            x:Name="MyBorder"
            BorderBrush="Black" 
            Background="AliceBlue"
            BorderThickness="3"/>
        <TextBox 
            x:Name="MyTextBox"
            HorizontalAlignment="Center" VerticalAlignment="Center"
            Text="{Binding Path=BorderThickness.Left, ElementName=MyBorder, Mode=OneWay}"/>
    </Grid>
</Window>

MainWindow.xaml.cs，在构造函数中：

MyTextBox.TextChanged += (sender, e) =>
{
    double d;
    if (!double.TryParse(MyTextBox.Text, out d)) return;
    var t = MyBorder.BorderThickness;
    t.Left = d;
    MyBorder.BorderThickness = t;
};

现在这对我有用，Robert Rossney的解决方案更好。

WPF：4个TextBoxes和1个Border.Margin之间的TwoWay绑定

3 个答案: