这将旋转整个ColumnHeaderCell：

This will rotate the whole ColumnHeaderCell:

<DataGrid.ColumnHeaderStyle>
    <Style TargetType="{x:Type DataGridColumnHeader}">
        <Setter Property="LayoutTransform">
            <Setter.Value>
                <RotateTransform Angle="270" />
            </Setter.Value>
        </Setter>
    </Style>
</DataGrid.ColumnHeaderStyle>

请注意：这意味着 Horizo​​ntalContentAlignment VerticalContentAlignment ，反之亦然。

Be aware: this means HorizontalContentAlignment is then a VerticalContentAlignment and vice versa.