wpf datagrid 的单元格内容超出列宽度

<Window x:Class="WpfApplication2.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <DataGrid Name="grid1" AutoGenerateColumns="False">
        <DataGrid.Columns>
            <!--自定义列-->
            <DataGridTemplateColumn Header="姓名" Width="30" MaxWidth="100">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate>
                        <!--设置当单元格内容超过最大长度时，显示...-->
                        <TextBlock Text="{Binding Name}" TextTrimming="WordEllipsis"/>
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
                <DataGridTemplateColumn.CellStyle>
                    <Style>
                         <!--加tooltip，显示单元格内容-->
                        <Setter Property="ToolTipService.ToolTip" Value="{Binding Name}"/>
                    </Style>
                </DataGridTemplateColumn.CellStyle>
            </DataGridTemplateColumn>
            <DataGridTextColumn Header="年龄" Binding="{Binding Age}" Width="50"/>
        </DataGrid.Columns>
    </DataGrid>
</Grid>