Question

HelloAll：我正在尝试创建一个用户控件，需要一个MultiValueConverter来扩展我的应用中的画布：

需要

Canvas.ActualWidth
X Min of Engineering units
X Max of Eng Units

OPENSSL_NO_PADDING

当我输入数字时，这似乎工作正常但是当我将XAML绑定到View模型时会出现问题：

这是错误消息：

错误7无法在“绑定”类型的“路径”属性上设置“绑定”。 '绑定'只能在DependencyObject的DependencyProperty上设置。 C：\ Users \ mwardell \ Documents \ Visual Studio 2013 \ Projects \ HalliburtonCallouts（12）\ HalliburtonCallouts \ HalliburtonCallouts \ View \ UserControls \ WellViewUserCtrl.xaml 31 38 HalliburtonCallouts

public class MultiValueScaleTransform : IMultiValueConverter
{
        public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
           double numerator     = (double)values[0];
           double denominator   = (double)values[2] - (double)values[1];
           return numerator / denominator;
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
        {
            throw new NotImplementedException();
        }
}

我已确定<UserControl x:Class="HalliburtonCallouts.View.UserControls.WellViewUserCtrl" 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:Converters="clr-namespace:HalliburtonCallouts.ViewModel.Converters" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" mc:Ignorable="d" d:DesignHeight="300" d:DesignWidth="300" x:Name="uc"> <UserControl.Resources> <Converters:ColorToImageBrush x:Key="ColorToBrush"/> <Converters:ColorToBitmapBrush x:Key="ColorToImg"/> <Converters:ColorToBG x:Key="ColorToBG"/> <Converters:ColorToFG x:Key="ColorToFG"/> <Converters:MultiValueScaleTransform x:Key="ScaleTransform"/> <SolidColorBrush x:Key="BlueBg" Color="#FFA9DCF1"/> </UserControl.Resources> <Border Background="Red"> <StackPanel>  <TextBlock Text="OverallStartDepth"></TextBlock> <TextBlock Text="{Binding OverallStartDepth}"></TextBlock> <TextBlock Text="OverallEndDepth"></TextBlock> <TextBlock Text="{Binding OverallEndDepth}"></TextBlock> <Canvas x:Name="WellCanvas" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" DataContext="{Binding Mode=OneWay, RelativeSource={RelativeSource PreviousData}}" > <Canvas.RenderTransform> <ScaleTransform > <ScaleTransform.ScaleX > <MultiBinding Converter="{StaticResource ScaleTransform}"> <Binding Path="ActualWidth"/> <Binding Path="{Binding OverallStartDepth, FallbackValue=0.0}"/> <Binding Path="{Binding OverallEndDepth,FallbackValue=100.0}"/> </MultiBinding> </ScaleTransform.ScaleX> </ScaleTransform> </Canvas.RenderTransform> </Canvas> </StackPanel> </Border> </UserControl>和OverallEndDepth是可绑定的。请参阅StackPanel前四项左右。不可绑定性证明它们是Dep Objects的Dep属性吗？

Answer 1

如错误所示，您不能使用{Binding}，而是可以通过其名称获取元素并从其text属性中获取值。

<TextBlock Text="OverallStartDepth"></TextBlock>
<TextBlock Name="OverallStartDepthTextBlock" Text="{Binding OverallStartDepth}"></TextBlock>
<TextBlock Text="OverallEndDepth"></TextBlock>
<TextBlock Name="OverallEndDepthTextBlock" Text="{Binding OverallEndDepth}"></TextBlock>
<MultiBinding Converter="{StaticResource ScaleTransform}">
    <Binding Path="ActualWidth"/>
    <Binding ElementName="OverallStartDepthTextBlock" Path="Text"/>
    <Binding ElementName="OverallEndDepthTextBlock" Path="Text"/>
</MultiBinding>

注意：您可以绑定OverallEndDepth是可绑定到任何控件的依赖项属性的值。

e.g。 TextBlock.Text是依赖属性 - SourceCode

/// <summary> /// DependencyProperty for <see cref="Text" /> property. /// </summary> [CommonDependencyProperty] public static readonly DependencyProperty TextProperty = DependencyProperty.Register( "Text", typeof(string), typeof(TextBlock), new FrameworkPropertyMetadata( string.Empty, FrameworkPropertyMetadataOptions.AffectsMeasure | FrameworkPropertyMetadataOptions.AffectsRender, new PropertyChangedCallback(OnTextChanged), new CoerceValueCallback(CoerceText))); /// <summary> /// The Text property defines the content (text) to be displayed. /// </summary> [Localizability(LocalizationCategory.Text)] public string Text { get { return (string) GetValue(TextProperty); } set { SetValue(TextProperty, value); } }

但是，Binding.Path是一个普通的属性，无法绑定，因此您得到上述错误 - SourceCode

/// <summary> The source path (for CLR bindings).</summary> public PropertyPath Path { get { return _ppath; } set { CheckSealed(); _ppath = value; _attachedPropertiesInPath = -1; ClearFlag(BindingFlags.PathGeneratedInternally); if (_ppath != null && _ppath.StartsWithStaticProperty) { if (_sourceInUse == SourceProperties.None || _sourceInUse == SourceProperties.StaticSource || FrameworkCompatibilityPreferences.TargetsDesktop_V4_0) // (for compat - Dev11 738992) { SourceReference = StaticSourceRef; } else throw new InvalidOperationException(SR.Get(SRID.BindingConflict, SourceProperties.StaticSource, _sourceInUse));> } } }

Answer 2

您无法在MultiBinding中绑定绑定的Path属性。相反，你只需在

中设置它们

<TextBlock Text="{Binding OverallStartDepth}">

相当于

<TextBlock Text="{Binding Path=OverallStartDepth}">

还有

<TextBlock>
    <TextBlock.Text>
        <Binding Path="OverallStartDepth"/>
    </TextBlock.Text>
</TextBlock>

因此MultiBinding应该像这样写：

<Canvas ... >
    <Canvas.RenderTransform>

        <MultiBinding Converter="{StaticResource ScaleTransform}">
            <Binding Path="ActualWidth" RelativeSource="{RelativeSource AncestorType=Canvas}"/>
            <Binding Path="OverallStartDepth" FallbackValue="0.0"/>
            <Binding Path="OverallEndDepth" FallbackValue="100.0"/>
        </MultiBinding>
    </Canvas.RenderTransform>
</Canvas>

还要确保删除

DataContext="{Binding Mode=OneWay, RelativeSource={RelativeSource PreviousData}}"

来自画布的

MultiValueConverter无法绑定到ViewModel

2 个答案: