将ToolTip绑定到自定义控件内的DependencyProperty

Question

我试图将一些值绑定到ToolTipService.ShowDuration和CellStyle的DataGridTextColumn中的一些其他ToolTip属性。

通常，我正在做这样的事情：

<UserControl
    ...namespace declarations...>
    <UserControl.Resources>
        <mycontrols:BindingProxy x:Key="proxy" Data="{Binding MySettings}"/>
    </UserControl.Resources>
    <DataGrid>
        <DataGridTextColumn
            Binding="{Binding SomeBinding}">
            <DataGridTextColumn.CellStyle>
                <Style 
                    TargetType="DataGridCell" 
                    BasedOn="{StaticResource ResourceKey={x:Type DataGridCell}}">
                    <Setter 
                        Property="ToolTipService.ShowDuration" 
                        Value="{Binding Data.ToolTipDuration, Source={StaticResource proxy}}"/>
                    <Setter Property="ToolTip">
                        <Setter.Value>
                            <TextBlock 
                                Text="{Binding SomeBinding}" 
                                MaxWidth="{Binding Data.ToolTipMaxWidth, Source={StaticResource proxy}}" 
                                TextWrapping="Wrap" TextTrimming="CharacterEllipsis"/>
                        </Setter.Value>
                    </Setter>
                </Style>
            </DataGridTextColumn.CellStyle>
        </DataGridTextColumn>
    </DataGrid>
</UserControl>

由于ToolTip有自己的可视化树，我使用这样的绑定代理：

public class BindingProxy : Freezable
    {
        protected override Freezable CreateInstanceCore()
        {
            return new BindingProxy();
        }

        public object Data
        {
            get { return (object)GetValue(DataProperty); }
            set { SetValue(DataProperty, value); }
        }

        // Using a DependencyProperty as the backing store for Data.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty DataProperty =
            DependencyProperty.Register("Data", typeof(object), typeof(BindingProxy), new UIPropertyMetadata(null));
    }

到目前为止，所有工作都按预期进行。但是我想重新使用这个DataGridTextColumn，所以我创建了这样的新文件：

<DataGridTextColumn
    x:Class="Test.MyControls.DataGridLargeTextColumn"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:Test.MyControls">
    <DataGridTextColumn.CellStyle>
        <Style 
            TargetType="DataGridCell" 
            BasedOn="{StaticResource ResourceKey={x:Type DataGridCell}}">
            <Setter 
                Property="ToolTipService.ShowDuration" 
                Value="{Binding ToolTipDuration}"/>
            <Setter Property="ToolTip">
                <Setter.Value>
                    <TextBlock 
                        Text="{Binding SomeBinding}" 
                        MaxWidth="{Binding ToolTipWidth}" 
                        TextWrapping="Wrap" TextTrimming="CharacterEllipsis"/>
                </Setter.Value>
            </Setter>
        </Style>
    </DataGridTextColumn.CellStyle>
</DataGridTextColumn>

代码背后：

public partial class DataGridLargeTextColumn : DataGridTextColumn
{
    public int ToolTipDuration
    {
        get { return (int)GetValue(ToolTipDurationProperty); }
        set { SetValue(ToolTipDurationProperty, value); }
    }
    public static readonly DependencyProperty ToolTipDurationProperty =
        DependencyProperty.Register("ToolTipDuration", typeof(int), typeof(DataGridLargeTextColumn), new UIPropertyMetadata(default(int)));

    public string SomeBinding
    {
        get { return (string)GetValue(SomeBindingProperty); }
        set { SetValue(SomeBindingProperty, value); }
    }
    public static readonly DependencyProperty SomeBindingProperty =
        DependencyProperty.Register("SomeBinding", typeof(string), typeof(DataGridLargeTextColumn), new UIPropertyMetadata(default(string)));

    public int ToolTipWidth
    {
        get { return (int)GetValue(ToolTipWidthProperty); }
        set { SetValue(ToolTipWidthProperty, value); }
    }
    public static readonly DependencyProperty ToolTipWidthProperty =
        DependencyProperty.Register("ToolTipWidth", typeof(int), typeof(DataGridLargeTextColumn), new UIPropertyMetadata(default(int)));

    public DataGridLargeTextColumn()
    {
        InitializeComponent();
    }
}

这不起作用，因为ToolTip有它自己的可视树，但由于我无处可放代理，我不知道如何使其工作或甚至可能。我找到了this answer，它似乎在正确的轨道上，然而，我试图像这样实现它，没有运气：

<Setter 
    Property="ToolTipService.ShowDuration"
    Value="{Binding Path=PlacementTarget.(local:DataGridLargeTextColumn.ToolTipDuration), RelativeSource={RelativeSource Self}}"/>
<Setter Property="ToolTip">
    <Setter.Value>
        <TextBlock 
            Text="{Binding Path=PlacementTarget.(local:DataGridLargeTextColumn.SomeBinding), RelativeSource={RelativeSource Self}}" 
            MaxWidth="{Binding Path=PlacementTarget.(local:DataGridLargeTextColumn.ToolTipWidth), RelativeSource={RelativeSource Self}}" 
            TextWrapping="Wrap" TextTrimming="CharacterEllipsis"/>
    </Setter.Value>
</Setter>

我使用PlacementTarget错了吗？如果没有，为什么它不起作用，还有另一种解决方案吗？

更新：

根据马克的回答，我修改了DataGridLargeTextColumn的风格：

<Style
    TargetType="DataGridCell" 
    BasedOn="{StaticResource {x:Type DataGridCell}}">
    <Setter 
        Property="ToolTipService.ShowDuration" Value="{Binding Path=PlacementTarget.ToolTipShowDuration, RelativeSource={x:Static RelativeSource.Self}}"/>
    <Setter Property="ToolTip">
        <Setter.Value>
            <ToolTip DataContext="{Binding Path=PlacementTarget, RelativeSource={x:Static RelativeSource.Self}}">
                <TextBlock 
                    Text="{Binding DataContext.SomeBinding}"
                    MaxWidth="{Binding Column.ToolTipWidth}"
                    TextWrapping="Wrap" TextTrimming="CharacterEllipsis"/>
            </ToolTip>
        </Setter.Value>
    </Setter>
</Style>

而我正在使用这样的控件：

<UserControl
    ...namespace declarations...>
    <UserControl.Resources>
        <mycontrols:BindingProxy x:Key="proxy" Data="{Binding MySettings}"/>
    </UserControl.Resources>
    <DataGrid>
        <DataGrid.Columns>
            <mycontrols:DataGridLargeTextColumn
                Binding="{Binding SomeBinding}"
                ToolTipShowDuration="{Binding Data.ToolTipDuration, Source={StaticResource proxy}}"
                ToolTipWidth="{Binding Data.ToolTipMaxWidth, Source={StaticResource proxy}}"/>
        </DataGrid.Columns>
    </DataGrid>
</UserControl>

宽度绑定现在就像魅力一样，但有两个问题我仍然无法解决：

1. 我无法获得工具提示持续时间来绑定，我尝试了几种不同的方法，但由于它是抽象的，因此无法明确声明
2. ToolTip的Text属性设置为SomeBinding，在这种特殊情况下可以，但是我希望能够将它设置为任何东西，所以我尝试使用上面的DependencProperty声明它，如下所示：

Text="{Binding Column.ToolTipText}"

如果我使用字符串文字，这可以正常工作：

<myControls:DataGridLargeTextColumn
    Binding="{Binding SomeBinding}"
    ToolTipText="12345"
    ToolTipShowDuration="{Binding Data.ToolTipDuration, Source={StaticResource proxy}}"
    ToolTipWidth="{Binding Data.ToolTipMaxWidth, Source={StaticResource proxy}}"/>

但是当我尝试绑定它时它不起作用，这正是我想要实现的：

<myControls:DataGridLargeTextColumn
    Binding="{Binding SomeBinding}"
    ToolTipText="{Binding SomeOtherPropertyBinding}" 
    ToolTipShowDuration="{Binding Data.ToolTipDuration, Source={StaticResource proxy}}"
    ToolTipWidth="{Binding Data.ToolTipMaxWidth, Source={StaticResource proxy}}"/>

Answer 1

默认情况下，ToolTip的DataContext设置为单元格的DataContext。但是，您正在尝试绑定到单元格列中的依赖项属性，因此您将不得不将DataContext更改为指向单元格本身，然后在您要访问数据时明确引用DataContext，当您访问Column时想要访问DataGridLargeTextColumn中的DP。

换句话说，除了内容之外，还要显式声明ToolTip并设置其DataContext，如下所示：

<Setter Property="ToolTip">
    <Setter.Value>
        <ToolTip DataContext="{Binding Path=PlacementTarget, RelativeSource={x:Static RelativeSource.Self}}">
            <TextBlock 
                Text="{Binding DataContext.SomeBinding}"
                Width="{Binding Column.ToolTipWidth}" />
        </ToolTip>
    </Setter.Value>
</Setter>

...在这种情况下，Text绑定到数据，Width绑定到自定义列DP。

或者你也可以按原样保留DataContext，而是使用ToolTip的Tag属性作为DataGridLargeTextColumn的绑定代理：

<Setter Property="ToolTip">
    <Setter.Value>
        <ToolTip Tag="{Binding Path=PlacementTarget.Column, RelativeSource={x:Static RelativeSource.Self}}">
            <TextBlock 
                Text="{Binding SomeBinding}"
                Width="{Binding Tag.ToolTipWidth, RelativeSource={RelativeSource AncestorType=ToolTip}}" />
        </ToolTip>
    </Setter.Value>
</Setter>