在WPF中获取DataGridTemplateColumn模板定义的内容控件

xaml格式描述：

<DataGrid Name="dataGrid" Grid.Row="1" ItemsSource="{Binding}" >
<DataGrid.Columns>
<DataGridTemplateColumn Header="描述">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<Expander x:Name="expander" Header="{Binding Describe}">
<TextBlock Text="{Binding Path=Exception}" TextWrapping="Wrap" MinHeight="30" MinWidth="250" />
</Expander>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
</DataGrid.Columns>
</DataGrid>

现在要获取expander控件，代码如下：

int index = dataGrid.CurrentCell.Column.DisplayIndex;

DataGridTemplateColumn templeColumn = dataGrid.Columns[index] as DataGridTemplateColumn;

if(templeColumn == null) return;

object item = dataGrid.CurrentCell.Item；

FrameworkElement element = templeColumn.GetCellContent(item);
Expander expander= templeColumn.CellTemplate.FindName("expander", element);