WPF 为什么我的 Line 对象没有改变位置？

Question

我想在一个图形中显示两条水平线。线的位置取决于一些数据。 为此，我创建了一个 ValueConverter（基本上是 int 的两倍）。问题是，线条总是显示在相同的位置。

我必须关注 XAML：

    <Window
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
            xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
            xmlns:local="clr-namespace:CGM_Auswertung"
            xmlns:chartingToolkit="clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVisualization.Toolkit" x:Class="CGM_Auswertung.MainWindow"
            mc:Ignorable="d"
            Title="MainWindow" Height="780" Width="1300" Loaded="Window_Loaded">
        <Window.Resources>
            <local:DoubleToPositionConverter x:Key="DtPConverter"/>
        </Window.Resources>
        <Grid Name="MainGrid">
            <StackPanel Margin="10" Orientation="Vertical">
                <Button Name="OpenFile" Content="Öffnen" Height="30" Margin="550,0" Click="OpenFile_Click"/>
                <Grid x:Name="drawGrid" >
                    <TextBox Height="30" Width="40" HorizontalAlignment="Left" VerticalAlignment="Top" Text="{Binding OptMinimum}"/>
                    <Frame x:Name="drawFrame" HorizontalAlignment="Left" Height="420" Margin="40,10,10,50" VerticalAlignment="Top" Width="1210" BorderBrush="Black" BorderThickness="3">
                        <Frame.Content>
                            <Grid Name="contentGrid" Background="Transparent" >
                                <Line x:Name="MinLine" Stroke="Red" StrokeThickness="2" StrokeDashArray="2,2" X1="0" X2="1200" Y1="{Binding OptMinimum, Converter={StaticResource DtPConverter}}" Y2="{Binding OptMinimum, Converter={StaticResource DtPConverter}}"/>
                                <Line x:Name="MaxLine" Stroke="Red" StrokeThickness="2" StrokeDashArray="2,2" X1="0" X2="1200" Y1="{Binding OptMaximum, Converter={StaticResource DtPConverter}}" Y2="{Binding OptMaximum, Converter={StaticResource DtPConverter}}"/>
                                <Grid Name="vertLineGrid" MouseMove="tempLineGrid_MouseMove" Background="Transparent" HorizontalAlignment="Center" VerticalAlignment="Center" Height="394" Width="1183" MouseUp="ReleaseSelectedItem"/>
                            </Grid>
                        </Frame.Content>
...

这是转换器：

namespace CGM_Auswertung
{
    public class ViewModelBase : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChanged(PropertyChangedEventArgs e)
        {
            PropertyChanged?.Invoke(this, e);
        }
    }

    public class ViewModel : ViewModelBase
    {
        ...

        private double _optMinimum;
        public double OptMinimum
        {
            get { return _optMinimum; }
            set
            {
                _optMinimum = value;
                OnPropertyChanged(new PropertyChangedEventArgs("OptMinimum"));
            }
        }

        private double _optMaximum;
        public double OptMaximum
        {
            get { return _optMaximum; }
            set
            {
                _optMaximum = value;
                OnPropertyChanged(new PropertyChangedEventArgs("OptMaximum"));
            }
        }


    }

    public class DoubleToPositionConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return (int)(Math.Abs(400 - (double)value * 20));
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return (double)(Math.Abs((double)value / 20 - 400 / 20));
        }
    }
}

我在转换器之前也试过这个：

[ValueConversion(typeof(double),typeof(int))]

但它并没有改变任何东西 这是我的程序的开始：

namespace CGM_Auswertung
{
    /// <summary>
    /// Interaktionslogik für MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        private List<CGM_Measurement> completeMeasures = new List<CGM_Measurement>();       
        private ViewModel mvm = new ViewModel() { MinimalValue = 0, MaximalValue=0, ActualValue=0};
        private UIElement selectedItem = null;

        public MainWindow()
        {
            mvm.FirstDay = mvm.LastDay = DateTime.Today;
            mvm.OverviewText = "Switch to day view";
            mvm.Visual = Visibility.Visible;
            mvm.VisualInverse = Visibility.Collapsed;
            mvm.OptMinimum = 2.0;
            mvm.OptMaximum = 3.0;

            InitializeComponent();

            MainGrid.DataContext = mvm;

        }

我猜问题出在 xaml 中，因为当我在转换器中设置断点时，不会调用转换。

我猜是因为转换非常简单，我可以在我的视图模型中使用另一个属性。但是由于我还在学习 WPF，所以我想用一个值转换器来做。

感谢您的帮助。

Answer 1

Frame 不继承父容器的 DataContext（在this SO post 中解释）。所以contentGrid 缺少绑定源。结果绑定没有被解析并且转换器没有被调用。尝试用 ContentControl 替换 Frame 或完全删除它