如何绑定DataGridColumn.Visibility？

Question

我有类似以下帖子的问题:

Silverlight DataGridTextColumn绑定可见性

我需要根据ViewModel中的值对Silverlight DataGrid中的列进行可见/折叠.为此,我尝试将Visibility属性绑定到ViewModel.但是我很快发现Visibility属性不是DependencyProperty,因此无法绑定.

为了解决这个问题,我尝试将自己的DataGridTextColumn子类化.有了这个新的类,我创建了一个DependencyProperty,最终推动更改DataGridTextColumn.Visibility财产.如果我没有数据绑定,这很有效.在我数据绑定到新属性的那一刻,它失败了,带有AG_E_PARSER_BAD_PROPERTY_VALUE异常.

public class MyDataGridTextColumn : DataGridTextColumn
{
    #region public Visibility MyVisibility

    public static readonly DependencyProperty MyVisibilityProperty =
        DependencyProperty.Register("MyVisibility", typeof(Visibility), typeof(MyDataGridTextColumn), new PropertyMetadata(Visibility.Visible, OnMyVisibilityPropertyChanged));

    private static void OnMyVisibilityPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var @this = d as MyDataGridTextColumn;

        if (@this != null)
        {
            @this.OnMyVisibilityChanged((Visibility)e.OldValue, (Visibility)e.NewValue);
        }
    }

    private void OnMyVisibilityChanged(Visibility oldValue, Visibility newValue)
    {
        Visibility = newValue;
    }

    public Visibility MyVisibility
    {
        get { return (Visibility)GetValue(MyVisibilityProperty); }
        set { SetValue(MyVisibilityProperty, value); }
    }

    #endregion public Visibility MyVisibility
}

这是XAML的一小部分.

<DataGrid ....>
    <DataGrid.Columns>
        <MyDataGridTextColumn Header="User Name"
                              Foreground="#FFFFFFFF"
                              Binding="{Binding User.UserName}"
                              MinWidth="150"
                              CanUserSort="True"
                              CanUserResize="False"
                              CanUserReorder="True"
                              MyVisibility="{Binding Converter={StaticResource BoolToVisibilityConverter}, Path=ShouldShowUser}"/>
        <DataGridTextColumn .../>
    </DataGrid.Columns>
</DataGrid>

一些重要的事实.

• 转换器确实在上面的本地资源中定义.
• 转换器是正确的,它在解决方案中的许多其他地方使用.
• 如果我将MyVisibility属性的{Binding}语法替换为"Collapsed",则Column确实会消失.
• 如果我创建一个新的DependencyProperty(即字符串Foo),并绑定到它,我也会收到AG_E_PARSER_BAD_PROPERTY_VALUE异常.

有没有人知道为什么这不起作用？

Answer 1

这是我用一点点黑客得出的解决方案.

首先,您需要从DataGrid继承.

public class DataGridEx : DataGrid
{
    public IEnumerable<string> HiddenColumns
    {
        get { return (IEnumerable<string>)GetValue(HiddenColumnsProperty); }
        set { SetValue(HiddenColumnsProperty, value); }
    }

    public static readonly DependencyProperty HiddenColumnsProperty =
        DependencyProperty.Register ("HiddenColumns", 
                                     typeof (IEnumerable<string>), 
                                     typeof (DataGridEx),
                                     new PropertyMetadata (HiddenColumnsChanged));

    private static void HiddenColumnsChanged(object sender,
                                             DependencyPropertyChangedEventArgs args)
    {
        var dg = sender as DataGrid;
        if (dg==null || args.NewValue == args.OldValue)
            return;

        var hiddenColumns = (IEnumerable<string>)args.NewValue;
        foreach (var column in dg.Columns)
        {
            if (hiddenColumns.Contains ((string)column.GetValue (NameProperty)))
                column.Visibility = Visibility.Collapsed;
            else
                column.Visibility = Visibility.Visible;
        }
    }
}

该DataGridEx类增加了新的DP隐藏基于列X:名称上的DataGridColumn及其后代.

要在您的XAML中使用:

<my:DataGridEx x:Name="uiData"
               DataContext="{Binding SomeDataContextFromTheVM}"
               ItemsSource="{Binding Whatever}"
               HiddenColumns="{Binding HiddenColumns}">
    <sdk:DataGridTextColumn x:Name="uiDataCountOfItems">
                            Header="Count"
                            Binding={Binding CountOfItems}"
    </sdk:DataGridTextColumn>
</my:DataGridEx>

您需要将这些添加到ViewModel或您使用的任何数据上下文.

private IEnumerable<string> _hiddenColumns;
public IEnumerable<string> HiddenColumns
{
    get { return _hiddenColumns; }
    private set
    {
        if (value == _hiddenColumns)
            return;

        _hiddenColumns = value;
        PropertyChanged (this, new PropertyChangedEventArgs("HiddenColumns"));
    }
}

public void SomeWhereInYourCode ()
{
    HiddenColumns = new List<string> {"uiDataCountOfItems"};
}

要取消隐藏,您只需要从列表中删除相应的名称,或者在没有隐藏名称的情况下重新创建它.

Answer 2

我有另一个解决此问题的方法,它使用类似于在DataGridTextColumn上找到的"绑定"属性的方法.由于列类是DependencyObjects,因此无法直接对它们进行数据绑定,但是如果添加对实现INotifyPropertyChanged的FrameworkElement的引用,则可以将数据绑定传递给元素,然后使用依赖项属性通知Column数据绑定已更改.

需要注意的一点是,对Column本身而不是Grid进行绑定可能意味着您将需要使用DataContextProxy来访问要将Visibility绑定到的字段(列绑定将默认为ItemSource的范围).

using System;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;

namespace XYZ.Controls
{
public class ExtendedDataGridTextColumn : DataGridTextColumn
{
    private readonly Notifier _e;

    private Binding _visibilityBinding;
    public Binding VisibilityBinding
    {
        get { return _visibilityBinding; }
        set
        {
            _visibilityBinding = value;
            _e.SetBinding(Notifier.MyVisibilityProperty, _visibilityBinding);
        }
    }

    public ExtendedDataGridTextColumn()
    {
        _e = new Notifier();
        _e.PropertyChanged += ToggleVisibility;
    }

    private void ToggleVisibility(object sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == "Visibility")
            this.Visibility = _e.MyVisibility;
    }

    //Notifier class is just used to pass the property changed event back to the column container Dependency Object, leaving it as a private inner class for now
    private class Notifier : FrameworkElement, INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public Visibility MyVisibility
        {
            get { return (Visibility)GetValue(MyVisibilityProperty); }
            private set { SetValue(MyVisibilityProperty, value); }
        }

        public static readonly DependencyProperty MyVisibilityProperty = DependencyProperty.Register("MyVisibility", typeof(Visibility), typeof(Notifier), new PropertyMetadata(MyVisibilityChanged));

        private static void MyVisibilityChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var n = d as Notifier;
            if (n != null)
            {
                n.MyVisibility = (Visibility) e.NewValue;
                n.PropertyChanged(n, new PropertyChangedEventArgs("Visibility"));
            }
        }
    }
}

}