WPF 写数据模板，需要重新指定数据上下文

<DataGridTemplateColumn Header="位置信息" Width="*">
    <DataGridTemplateColumn.CellTemplate>
        <DataTemplate>
                <Button Content="查看" Tag="{Binding ElementName=PhoneTextColumn}" x:Name="LocationButton"   DataContext="{Binding ElementName=FaUserControl,Path=DataContext}"
                    Style="{StaticResource NewBtStyle}">
                    <i:Interaction.Triggers>
                        <i:EventTrigger EventName="Click">
                            <ei:CallMethodAction MethodName="LocationButton_OnClick"  TargetObject="{Binding }" />
                        </i:EventTrigger>
                    </i:Interaction.Triggers>
                </Button>
        </DataTemplate>
    </DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>

FaUserControl为整个UserControl