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);