使用 IValueConverter 将列的宽度绑定到 DependencyProperty

Question

我正在尝试使网格元素中的列的宽度可变。为此，我有一个 DependencyProperty“ItemWidth”，并将 Width 元素从 Button 绑定到此 DP。由于 TwoWay-Binding，我需要一个将双精度数转换为 DataGridLength 的转换器。

我的 MainWindow.xaml 如下所示：

<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:utils="clr-namespace:WpfApplication1" Title="MainWindow" Height="350" Width="525">
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition />
        <ColumnDefinition />
    </Grid.ColumnDefinitions>
    <Grid.Resources>
        <utils:ColumnWidthConverter x:Key="columnWidthConverter"/>
    </Grid.Resources>
    <Button Grid.Row="0" Grid.Column="0" Width="{Binding Path=ItemWidth, Mode=TwoWay, Converter={StaticResource columnWidthConverter}}" Click="Shorter_Click">shorter</Button>
    <Button Grid.Row="0" Grid.Column="1" Width="{Binding Path=ItemWidth, Mode=TwoWay, Converter={StaticResource columnWidthConverter}}" Click="Longer_Click">longer</Button>
</Grid>
</Window>

ColumnWidthConverter.cs 如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows;

namespace WpfApplication1
{
    class ColumnWidthConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (value == null)
                return null;
            else
            {
                DataGridLengthConverter cv = new DataGridLengthConverter();
                object result = cv.ConvertFrom(value);
                return result;
            }

        }

        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (value == null)
                return null;
            else
            {
                DataGridLengthConverter cv = new DataGridLengthConverter();
                return cv.ConvertTo(value, typeof(double));
            }
        }
    }
}

MainWindow.xaml.cs 如下所示：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApplication1
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        public double ItemWidth
        {
            get { return (double)GetValue(ItemWidthProperty); }
            set { SetValue(ItemWidthProperty, value); }
        }

        public static readonly DependencyProperty ItemWidthProperty =
        DependencyProperty.Register("ItemWidth", typeof(double), typeof(MainWindow), new UIPropertyMetadata(0.0));

        private void Shorter_Click(object sender, RoutedEventArgs e)
        {
            this.ItemWidth -= 100;
        }

        private void Longer_Click(object sender, RoutedEventArgs e)
        {
            this.ItemWidth += 100;
        }
    }
}

因此，当我单击其中一个按钮时，按钮的宽度应该发生变化。但这并没有发生。你能告诉我这是为什么以及某种解决方案吗？

Answer 1

您在绑定中没有设置源，因此它是相对于 DataContext，您似乎没有在任何地方设置它，如果您添加它应该可以工作。例如，

<Window DataContext="{Binding RelativeSource={RelativeSource Self}}" ...

您可能想要（即您绝对应该）查看调试数据绑定（如果您不熟悉的话）。

你还绑定了不需要转换器的属性，实际上转换器可能会在这里引起问题，你不是想绑定ColumnDefinition.Width吗？

Answer 2

我将以下内容用于我的 GridSplitter

public class DoubleToGridLengthConverter : IValueConverter
{

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {

        double i = (double)value;

        GridLength result = new GridLength(i);

        return result;

    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {

        GridLength g = (GridLength)value;

        return (double)g.Value;

    }

}

xaml

Width="{Binding Source={x:Static Properties:Settings.Default}, Path=GridSplitter, Mode=TwoWay, Converter={StaticResource GridLengthConverter}}"