c# - 绑定到资源键，WPF

Question

我有一个带有一些图像的 ResourceDictionary：

<BitmapImage UriSource="..\Images\Bright\folder-bright.png"
             x:Key="FolderItemImage" />

我HierarchicalTemplate为树视图项目创建了一个，如下所示：

<HierarchicalDataTemplate ItemsSource="{Binding VisibleChildren}"
                          DataType="{x:Type st:StructureTreeItem}">
    <StackPanel Orientation="Horizontal">
        <TextBlock Text="{Binding ImageResourceKey}" />
        <Image x:Name="iIcon2" Source="{DynamicResource FolderItemImage}"/>
        <Image x:Name="iIcon"
               Source="{DynamicResource {Binding ImageResourceKey}}"/>
    </StackPanel>
</HierarchicalDataTemplate>

现在，当显示项目时：

文本块显示FolderItemImage
显示第一张图片
第二张图片没有显示。

整个想法是将项目图像设置为存储在资源中的图像，但不幸的是，上面介绍的技术不起作用，现在我知道了，为什么：

<Image x:Name="iIcon3" Width="16" Height="16" Margin="0, 1, 3, 1" >
    <Image.Source>
        <DynamicResource ResourceKey="{Binding ImageResourceKey}" />
    </Image.Source>
</Image>

结果：

PresentationFramework.dll 中出现“System.Windows.Markup.XamlParseException”类型的未处理异常

附加信息：不能在“DynamicResourceExtension”类型的“ResourceKey”属性上设置“绑定”。只能在 DependencyObject 的 DependencyProperty 上设置“绑定”。

所以我必须重新提出我的问题：如何将存储在模型中的一些数据（也许是资源键？）转换为动态资源？它必须是动态资源，因为我确信它可能会在运行时发生变化。

score 21 · Accepted Answer

我编写了以下标记扩展以允许在一般情况下绑定到 resourceKey

using System;
using System.ComponentModel;
using System.Globalization;
using System.Windows;
using System.Windows.Data;
using System.Windows.Markup;

namespace Mersoft.Mvvm.MarkupExtensions
{

    public class ResourceBinding : MarkupExtension
    {
        #region Helper properties

        public static object GetResourceBindingKeyHelper(DependencyObject obj)
        {
            return (object)obj.GetValue(ResourceBindingKeyHelperProperty);
        }

        public static void SetResourceBindingKeyHelper(DependencyObject obj, object value)
        {
            obj.SetValue(ResourceBindingKeyHelperProperty, value);
        }

        // Using a DependencyProperty as the backing store for ResourceBindingKeyHelper.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty ResourceBindingKeyHelperProperty =
            DependencyProperty.RegisterAttached("ResourceBindingKeyHelper", typeof(object), typeof(ResourceBinding), new PropertyMetadata(null, ResourceKeyChanged));

        static void ResourceKeyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var target = d as FrameworkElement;
            var newVal = e.NewValue as Tuple<object, DependencyProperty>;

            if (target == null || newVal == null)
                return;

            var dp = newVal.Item2;

            if (newVal.Item1 == null)
            {
                target.SetValue(dp, dp.GetMetadata(target).DefaultValue);
                return;
            }

            target.SetResourceReference(dp, newVal.Item1);

        }

        #endregion

        public ResourceBinding()
        {

        }

        public ResourceBinding(string path)
        {
            this.Path = new PropertyPath(path);
        }

        public override object ProvideValue(IServiceProvider serviceProvider)
        {
            var provideValueTargetService = (IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget));
            if (provideValueTargetService == null)
                return null;

            if (provideValueTargetService.TargetObject != null &&
                provideValueTargetService.TargetObject.GetType().FullName == "System.Windows.SharedDp")
                return this;


            var targetObject = provideValueTargetService.TargetObject as FrameworkElement;
            var targetProperty = provideValueTargetService.TargetProperty as DependencyProperty;
            if (targetObject == null || targetProperty == null)
                return null;



            var binding = new Binding();

            #region binding

            binding.Path = this.Path;
            binding.XPath = this.XPath;
            binding.Mode = this.Mode;
            binding.UpdateSourceTrigger = this.UpdateSourceTrigger;
            binding.Converter = this.Converter;
            binding.ConverterParameter = this.ConverterParameter;
            binding.ConverterCulture = this.ConverterCulture;

            if (this.RelativeSource != null)
                binding.RelativeSource = this.RelativeSource;

            if (this.ElementName != null)
                binding.ElementName = this.ElementName;

            if (this.Source != null)
                binding.Source = this.Source;

            binding.FallbackValue = this.FallbackValue;

            #endregion

            var multiBinding = new MultiBinding();
            multiBinding.Converter = HelperConverter.Current;
            multiBinding.ConverterParameter = targetProperty;

            multiBinding.Bindings.Add(binding);

            multiBinding.NotifyOnSourceUpdated = true;

            targetObject.SetBinding(ResourceBindingKeyHelperProperty, multiBinding);

            return null;

        }


        #region Binding Members

        /// <summary> The source path (for CLR bindings).</summary>
        public object Source
        {
            get;
            set;
        }

        /// <summary> The source path (for CLR bindings).</summary>
        public PropertyPath Path
        {
            get;
            set;
        }

        /// <summary> The XPath path (for XML bindings).</summary>
        [DefaultValue(null)]
        public string XPath
        {
            get;
            set;
        }

        /// <summary> Binding mode </summary>
        [DefaultValue(BindingMode.Default)]
        public BindingMode Mode
        {
            get;
            set;
        }

        /// <summary> Update type </summary>
        [DefaultValue(UpdateSourceTrigger.Default)]
        public UpdateSourceTrigger UpdateSourceTrigger
        {
            get;
            set;
        }

        /// <summary> The Converter to apply </summary>
        [DefaultValue(null)]
        public IValueConverter Converter
        {
            get;
            set;
        }

        /// <summary>
        /// The parameter to pass to converter.
        /// </summary>
        /// <value></value>
        [DefaultValue(null)]
        public object ConverterParameter
        {
            get;
            set;
        }

        /// <summary> Culture in which to evaluate the converter </summary>
        [DefaultValue(null)]
        [TypeConverter(typeof(System.Windows.CultureInfoIetfLanguageTagConverter))]
        public CultureInfo ConverterCulture
        {
            get;
            set;
        }

        /// <summary>
        /// Description of the object to use as the source, relative to the target element.
        /// </summary>
        [DefaultValue(null)]
        public RelativeSource RelativeSource
        {
            get;
            set;
        }

        /// <summary> Name of the element to use as the source </summary>
        [DefaultValue(null)]
        public string ElementName
        {
            get;
            set;
        }


        #endregion

        #region BindingBase Members

        /// <summary> Value to use when source cannot provide a value </summary>
        /// <remarks>
        ///     Initialized to DependencyProperty.UnsetValue; if FallbackValue is not set, BindingExpression
        ///     will return target property's default when Binding cannot get a real value.
        /// </remarks>
        public object FallbackValue
        {
            get;
            set;
        }

        #endregion



        #region Nested types

        private class HelperConverter : IMultiValueConverter
        {
            public static readonly HelperConverter Current = new HelperConverter();

            public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
            {
                return Tuple.Create(values[0], (DependencyProperty)parameter);
            }
            public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
            {
                throw new NotImplementedException();
            }
        }

        #endregion
    }
}

用法

<Image Source="{local:ResourceBinding ImageResourceKey}"/>

score 11 · Accepted Answer

它不能直接完成。尽管涉及附加属性，但还有另一种方法：

public static class ImageHelper {

    private static void SourceResourceKeyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {

        var element = d as Image;
        if (element != null) {

            element.SetResourceReference(Image.SourceProperty, e.NewValue);
        }
    }

    public static readonly DependencyProperty SourceResourceKeyProperty = DependencyProperty.RegisterAttached("SourceResourceKey",
        typeof(object),
        typeof(ImageHelper),
        new PropertyMetadata(String.Empty, SourceResourceKeyChanged));

    public static void SetSourceResourceKey(Image element, object value) {

        element.SetValue(SourceResourceKeyProperty, value);
    }

    public static object GetSourceResourceKey(Image element) {

        return element.GetValue(SourceResourceKeyProperty);
    }
}

接着：

<Image local:ImageHelper.SourceResourceKey="{Binding SomeValue}" />

score 7 · Accepted Answer

我认为不可能以您尝试这样做的方式使用动态字符串值作为字典的键。

您需要制作Converter从 a 转换为的 astring或ImageSource用于DataTrigger选择Source取决于ImageResourceKey

使用转换器：

在资源中：

<local:StringToResource x:Key="StringToResource" />

然后：

<Image x:Name="iIcon" Source="{Binding ImageResourceKey, Converter={StaticResource StringToResource}}"/>

您的转换器可能如下所示：

public class StringToResource: IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return Application.Current.FindResource(value as string);
    }

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

未测试

score 1 · Accepted Answer

public class DynamicResourceBinding : MarkupExtension
{
    public DynamicResourceBinding(string path)
    {
        binding = new Binding(path);
    }

    #region Binding Members

    public PropertyPath Path
    {
        get { return binding.Path; }
        set { binding.Path = value; }
    }
    public string XPath
    {
        get { return binding.XPath; }
        set { binding.XPath = value; }
    }
    [DefaultValue(BindingMode.Default)]
    public BindingMode Mode
    {
        get { return binding.Mode; }
        set { binding.Mode = value; }
    }
    [DefaultValue(UpdateSourceTrigger.Default)]
    public UpdateSourceTrigger UpdateSourceTrigger
    {
        get { return binding.UpdateSourceTrigger; }
        set { binding.UpdateSourceTrigger = value; }
    }
    public IValueConverter Converter
    {
        get { return binding.Converter; }
        set { binding.Converter = value; }
    }
    public object ConverterParameter
    {
        get { return binding.ConverterParameter; }
        set { binding.ConverterParameter = value; }
    }
    [TypeConverter(typeof(CultureInfoIetfLanguageTagConverter))]
    public CultureInfo ConverterCulture
    {
        get { return binding.ConverterCulture; }
        set { binding.ConverterCulture = value; }
    }
    public object Source
    {
        get { return binding.Source; }
        set { binding.Source = value; }
    }
    public string ElementName
    {
        get { return binding.ElementName; }
        set { binding.ElementName = value; }
    }
    public RelativeSource RelativeSource
    {
        get { return binding.RelativeSource; }
        set { binding.RelativeSource = value; }
    }
    public object FallbackValue
    {
        get { return binding.FallbackValue; }
        set { binding.FallbackValue = value; }
    }

    private readonly Binding binding;

    #endregion Binding Members

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        var provideValueTarget = serviceProvider.GetService(typeof(IProvideValueTarget)) as IProvideValueTarget;
        if (provideValueTarget != null)
        {
            var targetObject = provideValueTarget.TargetObject as FrameworkElement;
            if (targetObject != null)
            {
                var targetProperty = provideValueTarget.TargetProperty as DependencyProperty;
                if (targetProperty != null)
                {
                    targetObject.SetBinding(EnsureResourceKeyProperty(targetProperty), binding);
                }
            }
        }

        return null;
    }

    private static readonly object locker = new object();

    public static DependencyProperty EnsureResourceKeyProperty(DependencyProperty targetProperty)
    {
        DependencyProperty resourceKeyProperty;
        lock (locker)
        {
            if (!DirectMap.TryGetValue(targetProperty, out resourceKeyProperty))
            {
                resourceKeyProperty = RegisterResourceKeyProperty(targetProperty);
                DirectMap.Add(targetProperty, resourceKeyProperty);
                ReverseMap.Add(resourceKeyProperty, targetProperty);
            }
        }
        return resourceKeyProperty;
    }

    private static DependencyProperty RegisterResourceKeyProperty(DependencyProperty targetProperty)
    {
        return DependencyProperty.RegisterAttached(targetProperty.Name + "_ResourceKey", typeof(object), typeof(DynamicResourceBinding),
            new PropertyMetadata(ResourceKeyChanged));
    }

    private static void ResourceKeyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var fe = d as FrameworkElement;
        if (fe != null)
        {
            lock (locker)
            {
                DependencyProperty targetProperty;
                if (ReverseMap.TryGetValue(e.Property, out targetProperty))
                {
                    fe.SetResourceReference(targetProperty, e.NewValue);
                }
            }
        }
    }

    private static readonly Dictionary<DependencyProperty, DependencyProperty> DirectMap = new Dictionary<DependencyProperty, DependencyProperty>();
    private static readonly Dictionary<DependencyProperty, DependencyProperty> ReverseMap = new Dictionary<DependencyProperty, DependencyProperty>();
}

用法

c# - 绑定到资源键，WPF

4 回答 4

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