DataGridTextColumn 可见性绑定

Posted 2023-02-21

【中文标题】DataGridTextColumn 可见性绑定

【英文标题】：DataGridTextColumn Visibility Binding

【发布时间】：2012-02-09 11:37:59

【问题描述】：

我正在尝试将列可见性绑定到另一个元素的可见性，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"
    Title="MainWindow" Height="350" Width="525">
<Window.Resources>
    <BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" />
</Window.Resources>
<StackPanel>
    <CheckBox x:Name="chkColumnVisible" Content="Show column" />
    <DataGrid x:Name="MyDataGrid" AutoGenerateColumns="False">
        <DataGrid.Columns>
            <DataGridTextColumn Header="Column1" Visibility="Binding ElementName=chkColumnVisible, Path=IsChecked, Converter=StaticResource BooleanToVisibilityConverter"/>
        </DataGrid.Columns>
    </DataGrid>
</StackPanel>

但我在 VS 输出中收到此错误：

System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=IsChecked; DataItem=null; target element is 'DataGridTextColumn' (HashCode=48860040); target property is 'Visibility' (type 'Visibility')

有没有一种纯粹的 XAML 方法来实现这一点？

【参考方案1】：

DataGrid 的列是未出现在可视化或逻辑树中的抽象对象。您不能使用ElementName 和RelativeSource。 Source 与 x:Reference 结合应该可以工作：

Visibility="Binding Source=x:Reference chkColumnVisible,
                     Path=IsChecked,
                     Converter=StaticResource BooleanToVisibilityConverter"

【讨论】：

谢谢，它有效！但是这样我就可以睡觉了:)...我完全可以理解为什么 RelativeSource 不起作用，因为它是相对于目标的。但是ElementName到底有什么问题？我以为我通过使用 ElementName 为绑定提供了一个绝对源（显然我错了！）所以目标是否在可视树或逻辑树上都没有关系。

@ErenErsonmez：ElementName 使用当前的名称范围来解析名称，据我所知，名称范围依赖于树。

@ErenErsonmez: MSDN: You can refer to elements in code only if they are registered to the appropriate NameScope through RegisterName. For more information, see WPF XAML Namescopes -> The names in a XAML namescope can be used to establish relationships between the XAML-defined names of objects and their instance equivalents in an object tree.

谢谢！我知道除了使用代理元素之外，必须有更好的答案。

【参考方案2】：

我为它写了一个标记扩展：

using System;
using System.ComponentModel;
using System.Linq;
using System.Reflection;
using System.Windows;
using System.Windows.Data;
using System.Windows.Markup;
using System.Xaml;

/// <summary>
/// Binds to the datacontext of the current root object or ElementName
/// </summary>
[MarkupExtensionReturnType(typeof(object))]
public class NinjaBinding : MarkupExtension

    private static readonly DependencyObject DependencyObject = new DependencyObject();
    private static readonly string[] DoNotCopy =  "Path", "Source", "ElementName", "RelativeSource", "ValidationRules" ;
    private static readonly PropertyInfo[] CopyProperties = typeof(Binding).GetProperties().Where(x => !DoNotCopy.Contains(x.Name)).ToArray();
    public NinjaBinding()
    
    

    public NinjaBinding(Binding binding)
    
        Binding = binding;
    

    public Binding Binding  get; set; 

    private bool IsInDesignMode
    
        get  return DesignerProperties.GetIsInDesignMode(DependencyObject); 
    

    public override object ProvideValue(IServiceProvider serviceProvider)
    
        if (Binding == null)
        
            throw new ArgumentException("Binding == null");
        
        if (IsInDesignMode)
        
            return DefaultValue(serviceProvider);
        
        Binding binding = null;
        if (Binding.ElementName != null)
        
            var reference = new Reference(Binding.ElementName);
            var source = reference.ProvideValue(serviceProvider);
            if (source == null)
            
                throw new ArgumentException("Could not resolve element");
            
            binding = CreateElementNameBinding(Binding, source);
        
        else if (Binding.RelativeSource !=null)
        
            throw new ArgumentException("RelativeSource not supported");
        
        else
        
            var rootObjectProvider = (IRootObjectProvider)serviceProvider.GetService(typeof(IRootObjectProvider));
            if (rootObjectProvider == null)
            
                throw new ArgumentException("rootObjectProvider == null");
            
            binding = CreateDataContextBinding((FrameworkElement) rootObjectProvider.RootObject, Binding);
        

        var provideValue = binding.ProvideValue(serviceProvider);
        return provideValue;
    

    private static Binding CreateElementNameBinding(Binding original, object source)
    
        var binding = new Binding()
         
             Path = original.Path,
             Source = source,
         ;
        SyncProperties(original, binding);
        return binding;
    

    private static Binding CreateDataContextBinding(FrameworkElement rootObject, Binding original)
    
        string path = string.Format("0.1", FrameworkElement.DataContextProperty.Name, original.Path.Path);
        var binding = new Binding(path)
         
             Source = rootObject,
         ;
        SyncProperties(original, binding);
        return binding;
    

    private static void SyncProperties(Binding source, Binding target)
    
        foreach (var copyProperty in CopyProperties)
        
            var value = copyProperty.GetValue(source);
            copyProperty.SetValue(target, value);
        
        foreach (var rule in source.ValidationRules)
        
            target.ValidationRules.Add(rule);
        
    

    private static object DefaultValue(IServiceProvider serviceProvider)
    
        var provideValueTarget = (IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget));
        if (provideValueTarget == null)
        
            throw new ArgumentException("provideValueTarget == null");
        
        var dependencyProperty = (DependencyProperty)provideValueTarget.TargetProperty;
        return dependencyProperty.DefaultMetadata.DefaultValue;
    

它可以绑定到当前根对象 Window, UserControl, ...

的 DataContext

示例用法（可见性和可见性是 ViewModel 的属性）：

<DataGrid>
    <DataGrid.Columns>
        <DataGridTextColumn Header="DataContext" Visibility="dataGridBox:NinjaBinding Binding=Binding Visibility" />
        <DataGridTextColumn Header="Converter" Visibility="dataGridBox:NinjaBinding Binding=Binding Visible, Converter=StaticResource BooleanToVisibilityConverter" />
        <DataGridTextColumn Header="ElementName" Visibility="dataGridBox:NinjaBinding Binding=Binding IsChecked, ElementName=CheckBox, Converter=StaticResource BooleanToVisibilityConverter" />
    </DataGrid.Columns>
</DataGrid>

【讨论】：

由于某种原因对我不起作用...BindingExpression path error: 'ValidationColumnVisibility' property not found on 'object' ''NameFixupToken' (HashCode=55620207)'. BindingExpression:Path=ValidationColumnVisibility; DataItem='NameFixupToken' (HashCode=55620207); target element is 'DataGridTextColumn' (HashCode=62066456); target property is 'Visibility' (type 'Visibility')

在我的应用程序中完美地使用了 DataTemplateColumn 和 DataGrid。

【参考方案3】：

Johan Larsson 的解决方案完美运行，只有来自 Binding 的 FallbackValue 没有被转发，所以我将其更改为：

private object DefaultValue(IServiceProvider serviceProvider)

    if (Binding.FallbackValue != null)
        return Binding.FallbackValue;

    var provideValueTarget = (IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget));
    if (provideValueTarget == null)
    
        throw new ArgumentException("provideValueTarget == null");
    
    var dependencyProperty = (DependencyProperty)provideValueTarget.TargetProperty;
    return dependencyProperty.DefaultMetadata.DefaultValue;

所以它可以像这样使用，这里以绑定到 Header 为例：

<DataGridTemplateColumn Header="dataGridBox:NinjaBinding Binding=Binding MyHeaderName1, FallbackValue=HeadingNr1" />