新项目的组合框默认值

Question

I have 2 comboboxs that has it's itemssource bound to 2 lists which are in a listview. This all works fine however when I add a new new item to the list the combobox values are blank and I want them to show me "All Zones" for one and "All Facies" in the other. How do I get this to work? I have tried many examples but all want me to use the "IsSynchronizedWithCurrentItem" to be true or the SelectedIndex to 0 however this also sets the current combobox values to the SelectedIndex which is not what I want I only want it if the combobox is blank. Can anyone please help me?

Combobox's inside the ListView

<GridViewColumn Width="100">
                            <GridViewColumn.CellTemplate>
                                <DataTemplate>
                                    <ComboBox Style="{DynamicResource ComboBoxStyle1}" x:Name="zoneComboBox" Margin="0,0,5,0" Height="20" Width="80" ItemsSource="{Binding DataContext.Zones, RelativeSource={RelativeSource AncestorType={x:Type ListBox}, Mode=FindAncestor}}" SelectedValue="{Binding Zone}" SelectedIndex="0"/>
                                </DataTemplate>
                            </GridViewColumn.CellTemplate>
                            <GridViewColumnHeader>
                                <TextBlock Text="Zones" FontFamily="{DynamicResource FontFamily}" FontSize="11" FontWeight="Bold"/>
                            </GridViewColumnHeader>
                        </GridViewColumn>
                        <GridViewColumn Width="100">
                            <GridViewColumn.CellTemplate>
                                <DataTemplate>
                                    <ComboBox Style="{DynamicResource ComboBoxStyle1}" x:Name="faciesComboBox" Margin="0,0,5,0" Height="20" Width="80" ItemsSource="{Binding DataContext.Facies, RelativeSource={RelativeSource AncestorType={x:Type ListBox}, Mode=FindAncestor}}" SelectedValue="{Binding Facie}" SelectedIndex="0"/>
                                </DataTemplate>
                            </GridViewColumn.CellTemplate>
                            <GridViewColumnHeader>
                                <TextBlock Text="Facies" FontFamily="{DynamicResource FontFamily}" FontSize="11" FontWeight="Bold"/>
                            </GridViewColumnHeader>
                        </GridViewColumn>

Add new rule method

private void AddRuleBtn_Click(object sender, RoutedEventArgs e)
    {
        rules.Add(new GeologicalAnalysisRule());
    }

Observable Collection (Edit)

private ObservableCollection<GeologicalAnalysisRule> rules;

    public RuleSetterControl()
    {
        InitializeComponent();
        Rules = new ObservableCollection<GeologicalAnalysisRule>();
        Rules.Add(new GeologicalAnalysisRule());
    }

    public ObservableCollection<GeologicalAnalysisRule> Rules
    {
        get { return rules; }
        set
        {
            if (Equals(value, rules)) return;
            rules = value;
            OnPropertyChanged();
        }
    }

Answer 1

Instead of using private variable rules use Property Rules in the button click event.

private void AddRuleBtn_Click(object sender, RoutedEventArgs e)
{
    Rules.Add(new GeologicalAnalysisRule());
}