Adding groups with items to WPF ListView

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C#

WPF

Right, I have been trying for hours to do this with not much success. What I want to do is when the user clicks a button it should load a listview with a few groups (with expanders in(style is below)) then add a few items to the groups with there being an item and a subitem with it. The following code is the XAML for the style of the listview items:

<ListView Height="Auto" HorizontalAlignment="Left" Margin="1149,0,0,0" Name="dataTree" VerticalAlignment="Stretch" Width="292">
            <ListView.GroupStyle>
                <GroupStyle HidesIfEmpty="False">
                    <GroupStyle.ContainerStyle>
                        <Style TargetType="GroupItem">
                            <Setter Property="Template">
                                <Setter.Value>
                                    <ControlTemplate TargetType="GroupItem">
                                        <Expander IsExpanded="True">
                                            <Expander.Header>
                                                <Bold>
                                                    <TextBlock Text="{Binding Name}"/>
                                                </Bold>
                                            </Expander.Header>
                                            <ItemsPresenter/>
                                        </Expander>
                                    </ControlTemplate>
                                </Setter.Value>
                            </Setter>
                        </Style>
                    </GroupStyle.ContainerStyle>
                </GroupStyle>
            </ListView.GroupStyle>
            <ListView.View>
                <GridView>
                    <GridViewColumn Header="Parameter" Width="150" DisplayMemberBinding="{Binding Param}"/>
                    <GridViewColumn Header="Value" Width="100" DisplayMemberBinding="{Binding (originally 'group.Param' but not sure how this part works)}" />
                </GridView>
            </ListView.View>
        </ListView>

Basically I just want to know how to add groups and items to them to a listview in WPF. Much harder than windows forms. Thank you.