Select cells under expanded WPF datagrid with a button

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C#

WPF

I have the following code that creates wpf datagrid with an expander and a button using a Collection view in the cobe behind. I would like to know, how do I select the rows in the expanded group when the Accept Button is clicked.;

<Window.Resources>
        <DataTemplate x:Key="AcceptButton">
            <Button Width="80" Height="20" Content="Accept" Click="Button_Click" />
        </DataTemplate>
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <Button x:Name="cmdLogin" Content="About" HorizontalAlignment="Left" Margin="1205,13,0,0" VerticalAlignment="Top" Width="55" Background="#FF3DB1C8" FontWeight="Bold" Click="cmdLogin_Click"/>
        <DataGrid x:Name="dgFIFO" HorizontalAlignment="Left" Margin="150,73,0,0" VerticalAlignment="Top" Height="595" Width="430" ItemsSource="{Binding}" RowDetailsVisibilityMode="Visible">
            <DataGrid.GroupStyle>
                <!-- Style for groups at top level. -->
                <GroupStyle>
                    <GroupStyle.ContainerStyle>
                        <Style TargetType="{x:Type GroupItem}">
                            <Setter Property="Template">
                                <Setter.Value>
                                    <ControlTemplate TargetType="{x:Type GroupItem}">
                                        <Expander IsExpanded="True"  Background="#83D744" HeaderTemplate="{DynamicResource AcceptButton}"   >
                                            <Expander.Header>
                                                <DockPanel Height="25">
                                                    <TextBlock FontWeight="Bold" FontSize="12" Height="15"  Foreground="Black" Text="{Binding Path=Name,StringFormat= AcctNum:# {0}}" />
                                                </DockPanel>
                                            </Expander.Header>
                                            <Expander.Content>
                                                <ItemsPresenter />
                                            </Expander.Content>
                                        </Expander>
                                    </ControlTemplate>
                                </Setter.Value>
                            </Setter>
                        </Style>
                    </GroupStyle.ContainerStyle>
                </GroupStyle>
            </DataGrid.GroupStyle>

private void cmdProbReview_Click(object sender, RoutedEventArgs e)
        {
            BusinessTier.BLLProbs objbllprobs = new BusinessTier.BLLProbs();
            BusinessTier.Probs objprobs = new BusinessTier.Probs();
            DataSet dsData = new DataSet();

            objprobs.Status = cboStatus.SelectedValue.ToString();
            objprobs.Team = cboTeam.SelectedValue.ToString();

           try
            {
                dsData = objbllprobs.Select_wfSISProbs(objprobs.Status,objprobs.Team);
                
                myprobs.Source = dsData.Tables[0];
                myprobs.GroupDescriptions.Add(new PropertyGroupDescription("AcctNumber"));
                dgFIFO.ItemsSource = myprobs.View;
                
                
            }
            catch(ApplicationException ex)
            {
                System.Windows.MessageBox.Show(ex.Message);
            }
              
        }

What I have tried:

Have not tried much of anything, other then using the collectionview, but at a loss on how to start.