更改绑定值，而不是绑定本身

Question

我有一个包含 DependencyProperty (MyProperty) 的 WPF UserControl。

DependencyProperty 绑定到 DataContext 中的属性。

现在在 UserControl 中我想更改绑定属性的值。但是，如果我分配 MyProperty = NewValue 绑定就会丢失并被 NewValue 取代。

我想要实现的是更改 DependencyProperty 所绑定的 DataContext 属性。

我如何实现这一目标而不是更改绑定？

澄清一下：使用类似 MyTextBox.Text = "0"; 我将释放绑定。我将如何设置 Text，保持绑定不变，以便 Text 绑定的属性也会改变。

Answer 1

您可以使用SetCurrentValue。

SetCurrentValue 方法更改属性的有效值，但现有触发器、数据绑定和样式将继续工作。

Answer 2

如果没有看到你的代码，我无法判断你做错了什么。下面是一个简单的用户控件，允许用户选择颜色。

<UserControl x:Class="ColorPickerTest.ColorPicker"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

    <StackPanel Orientation="Horizontal">
        <ToggleButton Name="redButton" Content="Red" Click="Button_Click" />
        <ToggleButton Name="yellowButton" Content="Yellow" Click="Button_Click" />
    </StackPanel>
</UserControl>

using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;

namespace ColorPickerTest
{
    public partial class ColorPicker : UserControl
    {
        public ColorPicker()
        {
            InitializeComponent();
        }

        public Brush SelectedColor
        {
            get { return (Brush)GetValue(SelectedColorProperty); }
            set { SetValue(SelectedColorProperty, value); }
        }

        public static readonly DependencyProperty SelectedColorProperty =
            DependencyProperty.Register("SelectedColor", 
                                        typeof(Brush), 
                                        typeof(ColorPicker), 
                                        new UIPropertyMetadata(Brushes.Transparent, OnPropertyChanged));

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            if (!redButton.IsChecked.GetValueOrDefault() && !yellowButton.IsChecked.GetValueOrDefault())
            {
                SelectedColor = Brushes.Transparent;
            }
            else if (!redButton.IsChecked.GetValueOrDefault() && yellowButton.IsChecked.GetValueOrDefault())
            {
                SelectedColor = Brushes.Yellow;
            }
            else if (redButton.IsChecked.GetValueOrDefault() && !yellowButton.IsChecked.GetValueOrDefault())
            {
                SelectedColor = Brushes.Red;
            }
            else
            {
                // redButton.IsChecked.GetValueOrDefault() && yellowButton.IsChecked.GetValueOrDefault())

                SelectedColor = Brushes.Orange;
            }
        }

        private static void OnPropertyChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            ColorPicker colorPicker = sender as ColorPicker;
            colorPicker.redButton.IsChecked = colorPicker.SelectedColor == Brushes.Red ||
                                              colorPicker.SelectedColor == Brushes.Orange;
            colorPicker.yellowButton.IsChecked = colorPicker.SelectedColor == Brushes.Yellow ||
                                                 colorPicker.SelectedColor == Brushes.Orange;
        }
    }
}

<Window x:Class="ColorPickerTest.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:ColorPickerTest="clr-namespace:ColorPickerTest"
    Height="300" Width="300">
    <StackPanel>
        <ColorPickerTest:ColorPicker SelectedColor="{Binding Path=MyColor, Mode=TwoWay}" />
    </StackPanel>
</Window>

using System.Windows;
using System.Windows.Media;

namespace ColorPickerTest
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();

            MyColor = Brushes.Red;

            DataContext = this;
        }

        private Brush _myColor;
        public Brush MyColor
        {
            get { return _myColor; }
            set 
            {
                _myColor = value;
                Background = _myColor;
            }
        }
    }
}

Answer 3

这应该按原样工作，唯一的问题是当文本框失去焦点时，文本框绑定到的绑定源将被更新。这是默认行为。您可以通过在绑定中指定 UpdateSourceTrigger=PropertyChanged 来更改它。就像这样：

<TextBox Name="MyTextBox" Text="{Binding YourBindingPath, UpdateSourceTrigger=PropertyChanged}"/>