I need the Expand / Collapse for RowDetailsTemplate

I have a DataGrid. It has DataGrid.RowDetailsTemplate. When a button is clicked it should Expand / Collapse; how would I do that?

<Custom:DataGrid RowDetailsVisibilityMode="VisibleWhenSelected" SelectionMode="Extended" CanUserAddRows="False" CanUserDeleteRows="False" CanUserResizeRows="False" CanUserSortColumns="False">
    <Custom:DataGrid.RowDetailsTemplate>
        <DataTemplate>
            <Custom:DataGrid>
                <Custom:DataGrid.Columns>
                    <Custom:DataGridTextColumn Binding="{Binding idClient, Mode=Default}" Header="Ид" IsReadOnly="True"/>
                    <Custom:DataGridTextColumn Binding="{Binding name_client, Mode=Default}"  Header="Имя" IsReadOnly="True"/>
                </Custom:DataGrid.Columns>
            </Custom:DataGrid>
        </DataTemplate>
    </Custom:DataGrid.RowDetailsTemplate>
    <Custom:DataGrid.Columns>
        <Custom:DataGridTemplateColumn>
            <Custom:DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <Expander IsExpanded="True"/>
                </DataTemplate>
            </Custom:DataGridTemplateColumn.CellTemplate>
        </Custom:DataGridTemplateColumn>
        <Custom:DataGridTextColumn Binding="{Binding idPartner, Mode=Default}" Header="Ид" IsReadOnly="True"/>
        <Custom:DataGridTextColumn Binding="{Binding name_partner, Mode=Default}"  Header="Имя" IsReadOnly="True"/>
    </Custom:DataGrid.Columns>
</Custom:DataGrid>

Check this ...

Adding a Button to a WPF DataGrid

OR

XAML :

<DataGrid Name="dg1" AutoGenerateColumns="False" SelectionMode="Single" CanUserAddRows="false" CanUserDeleteRows="False" SelectionUnit="FullRow" >
    <DataGrid.CellStyle>
        <Style TargetType="DataGridCell">
            <Setter Property="BorderThickness" Value="0"/>
        </Style>
    </DataGrid.CellStyle>

    <DataGrid.RowHeaderTemplate>
        <DataTemplate>
            <Expander Expanded="Expander_Expanded" Collapsed="Expander_Collapsed">

            </Expander>
        </DataTemplate>
    </DataGrid.RowHeaderTemplate>

    <DataGrid.Columns>
        <DataGridTextColumn Header="Name" IsReadOnly="True" Width="100" Binding="{Binding Name}" />
        <DataGridTextColumn Header="Title" IsReadOnly="True" Width="100" Binding="{Binding Title}" />
        <DataGridTextColumn Header="Job" IsReadOnly="True" Width="100" Binding="{Binding Job}" />
    </DataGrid.Columns>

    <DataGrid.RowDetailsTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Isi, Converter={StaticResource ResourceKey=isiTextConverter}}" Margin="10,5,0,0" />
        </DataTemplate>
    </DataGrid.RowDetailsTemplate>
</DataGrid>

MainWindow.xaml.cs

private void Expander_Expanded(object sender, RoutedEventArgs e)
{
    for (var vis = sender as Visual; vis != null; vis = VisualTreeHelper.GetParent(vis) as Visual)
    if (vis is DataGridRow)
    {
        var row = (DataGridRow)vis;
        row.DetailsVisibility = row.DetailsVisibility == Visibility.Visible ? Visibility.Collapsed : Visibility.Visible;
        break;
    }
}

private void Expander_Collapsed(object sender, RoutedEventArgs e)
{
    for (var vis = sender as Visual; vis != null; vis = VisualTreeHelper.GetParent(vis) as Visual)
        if (vis is DataGridRow)
        {
            var row = (DataGridRow)vis;
            row.DetailsVisibility = row.DetailsVisibility == Visibility.Visible ? Visibility.Collapsed : Visibility.Visible;
            break;
        }
}

Output