在一个影响另一个对象的对象上创建一个简单的wpf触发器

Question

这是我最接近创建一个简单的触发器.我只想要datagrid的IsMouseOver == true来显示按钮.问题是Setter的TargetName说:属性'TargetName'不代表'Setter'的有效目标,因为找不到名为'ButtonExpand'的元素.确保在使用目标的任何Setter,Triggers或Conditions之前声明目标.我究竟做错了什么？

<UserControl.Resources>
    <Style TargetType="DataGrid">
        <Style.Triggers>
            <Trigger Property="IsMouseOver" Value="True">
                <Setter TargetName="ButtonExpand" Property="Visibility" Value="Visible" />
            </Trigger>
        </Style.Triggers>
    </Style>
</UserControl.Resources>
<Grid>



    <DataGrid Name="MainDataGrid" ItemsSource="{Binding Programs}" IsReadOnly="True" AutoGenerateColumns="false" >
        <DataGrid.Columns>
            <DataGridTextColumn Header="Name" Binding="{Binding Name}"/>
            <DataGridTextColumn Header="Version" Binding="{Binding Version}"/>
            <DataGridTextColumn Header="Publisher" Binding="{Binding Publisher}"/>
        </DataGrid.Columns>
    </DataGrid>

    <Button Name="ButtonExpand" Height="25" Width="25" HorizontalAlignment="Right" VerticalAlignment="Bottom" Visibility="Hidden">+</Button>
</Grid>

Answer 1

TargetName不适用于Style的Triggers集合.样式没有名称范围,因此在那里按名称引用元素没有意义.但是模板(DataTemplate或ControlTemplate)确实有一个名称范围.

看到这个链接.

您可以使用Button的DataTrigger进行相反的操作.请注意,必须在Style中设置Property Visibility才能使DataTrigger正常工作.

<Grid Name="MainGrid"> 

    <DataGrid ItemsSource="{Binding Programs}"
              IsReadOnly="True"
              AutoGenerateColumns="false" > 
      <DataGrid.Columns> 
        <DataGridTextColumn Header="Name" Binding="{Binding Name}"/> 
        <DataGridTextColumn Header="Version" Binding="{Binding Version}"/> 
        <DataGridTextColumn Header="Publisher" Binding="{Binding Publisher}"/> 
      </DataGrid.Columns> 
    </DataGrid> 

    <Button Name="ButtonExpand"
            Height="25"
            Width="25"
            HorizontalAlignment="Right"
            VerticalAlignment="Bottom"
            Content="+">
        <Button.Style>
            <Style TargetType="Button">
                <Setter Property="Visibility" Value="Hidden"/>
                <Style.Triggers>
                    <DataTrigger Binding="{Binding ElementName=MainGrid,
                                                   Path=IsMouseOver}" 
                                 Value="True">
                        <Setter Property="Visibility" Value="Visible" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Button.Style>
    </Button>
</Grid>

另一种方法是使用转换器将ButtonExpand的Visibilty绑定到DataGrid的IsMouseOver属性.