如何根据DataGridColumn类型对齐列头文本？已用触发器但未生效

问题背景 #

需求为：让DataGridComboBoxColumn的列头文本左对齐，其余类型DataGridColumn的列头文本居中。尝试两种Style触发器实现均未生效，相关代码如下：

<Window.Resources>
    <Style  x:Key="CustomColumnHeaderStyle1" TargetType="{x:Type DataGridColumnHeader}">
        <Setter Property="HorizontalContentAlignment"  Value="Center" />
        <Setter Property="Width" Value="200"/>
        <Style.Triggers>
            <DataTrigger Binding="{Binding DataContext, RelativeSource={RelativeSource Self}}" Value="{x:Type DataGridComboBoxColumn}">
                <Setter Property="HorizontalContentAlignment" Value="Left" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
    <Style  x:Key="CustomColumnHeaderStyle2" TargetType="{x:Type DataGridColumnHeader}">
        <Setter Property="HorizontalContentAlignment" Value="Center" />
        <Setter Property="Width" Value="200"/>
        <Style.Triggers>
            <DataTrigger Binding="{Binding Column}" Value="{x:Type DataGridComboBoxColumn}">
                <Setter Property="HorizontalContentAlignment" Value="Left" />
            </DataTrigger>
        </Style.Triggers>
    </Style>

    <ObjectDataProvider x:Key="myEnum" MethodName="GetValues" ObjectType="{x:Type core:Enum}">
        <ObjectDataProvider.MethodParameters>
            <x:Type Type="local:OrderStatus"/>
        </ObjectDataProvider.MethodParameters>
    </ObjectDataProvider>
</Window.Resources>
<Window.DataContext>
    <local:ViewModel/>
</Window.DataContext>
<Grid>
    <DataGrid ItemsSource="{Binding MyData}"  AutoGenerateColumns="False"
              ColumnHeaderStyle="{StaticResource CustomColumnHeaderStyle2}">
        <DataGrid.Columns>
            <DataGridComboBoxColumn Header="Order Status"  SelectedItemBinding="{Binding Status}" ItemsSource="{Binding Source={StaticResource myEnum}}" />
            <DataGridTextColumn Header="Text Column" Binding="{Binding Name}"/>
        </DataGrid.Columns>
    </DataGrid>
</Grid>

失效原因分析 #

CustomColumnHeaderStyle1 失效原因 #

触发器绑定{Binding DataContext, RelativeSource={RelativeSource Self}}，但DataGridColumnHeader的DataContext继承自DataGrid的DataContext（即ViewModel实例），并非当前列对象，因此无法获取列类型，触发器永远无法触发。

CustomColumnHeaderStyle2 失效原因 #

触发器绑定Column属性的方向是正确的，但Value="{x:Type DataGridComboBoxColumn}"是在类型对象和列实例对象之间做比较：Column是DataGridComboBoxColumn的实例，而Value是Type类型的对象，两者类型不匹配，条件永远不成立，触发器无法触发。

解决方案 #

方法1：使用类型转换转换器 #

通过转换器将列实例转换为对应的类型对象，再与目标类型比较：

1. 创建类型转换转换器

using System;
using System.Windows.Data;

namespace YourNamespace
{
    public class ObjectToTypeConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return value?.GetType();
        }

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

2. 修改XAML资源和样式

<Window.Resources>
    <local:ObjectToTypeConverter x:Key="ObjectToTypeConverter"/>
    
    <Style x:Key="CustomColumnHeaderStyle" TargetType="{x:Type DataGridColumnHeader}">
        <Setter Property="HorizontalContentAlignment" Value="Center" />
        <Setter Property="Width" Value="200"/>
        <Style.Triggers>
            <DataTrigger Binding="{Binding Column, Converter={StaticResource ObjectToTypeConverter}}" 
                         Value="{x:Type DataGridComboBoxColumn}">
                <Setter Property="HorizontalContentAlignment" Value="Left" />
            </DataTrigger>
        </Style.Triggers>
    </Style>

    <ObjectDataProvider x:Key="myEnum" MethodName="GetValues" ObjectType="{x:Type core:Enum}">
        <ObjectDataProvider.MethodParameters>
            <x:Type Type="local:OrderStatus"/>
        </ObjectDataProvider.MethodParameters>
    </ObjectDataProvider>
</Window.Resources>

3. 应用样式到DataGrid

<DataGrid ItemsSource="{Binding MyData}" AutoGenerateColumns="False"
          ColumnHeaderStyle="{StaticResource CustomColumnHeaderStyle}">
    <DataGrid.Columns>
        <DataGridComboBoxColumn Header="Order Status" SelectedItemBinding="{Binding Status}" ItemsSource="{Binding Source={StaticResource myEnum}}" />
        <DataGridTextColumn Header="Text Column" Binding="{Binding Name}"/>
    </DataGrid.Columns>
</DataGrid>

方法2：直接绑定列的类型（WPF 4.5+） #

若使用WPF 4.5及以上版本，可直接通过Path访问列实例的GetType()方法，无需转换器：

<Style x:Key="CustomColumnHeaderStyle" TargetType="{x:Type DataGridColumnHeader}">
    <Setter Property="HorizontalContentAlignment" Value="Center" />
    <Setter Property="Width" Value="200"/>
    <Style.Triggers>
        <DataTrigger Binding="{Binding Column.GetType()}" 
                     Value="{x:Type DataGridComboBoxColumn}">
            <Setter Property="HorizontalContentAlignment" Value="Left" />
        </DataTrigger>
    </Style.Triggers>
</Style>

内容的提问来源于stack exchange，提问作者wpf