如何仅在初始化期间调用转换器？

Question

我有一个包含转换器的项目。当我点击DGKraj（众多ComboBox中的一个）并在初始化期间自动调用转换器。如何仅在初始化期间调用转换器？

public class CountrySingleConverter : IValueConverter
{
    Funkcje FK = new Funkcje();
    List<string> kraje = new List<string>();

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {    
        if (value != null && !string.IsNullOrWhiteSpace(value.ToString()))
        { 
            kraje = FK.kraj_wybierz(value.ToString(), Edycja.dgKraj);
                return kraje;
        }
        return null;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }      
}

XAML

                        <DataGridComboBoxColumn x:Name="DGKraj" Header="Kraj" Width="120" CanUserSort="False" SelectedValueBinding="{Binding Kraj}" >
                            <DataGridComboBoxColumn.ElementStyle>
                                <Style TargetType="ComboBox">
                                    <Setter Property="ItemsSource" Value="{Binding Path=Kontynent,Converter={StaticResource CountryConverter}}"/>
                                    <Setter Property="SelectedValue" Value="{Binding Path=Kraj}"/>
                                </Style>
                            </DataGridComboBoxColumn.ElementStyle>
                            <DataGridComboBoxColumn.EditingElementStyle>
                                <Style TargetType="ComboBox">
                                    <Setter Property="ItemsSource" Value="{Binding Path=Kontynent,Converter={StaticResource CountryConverter}}" />
                                    <Setter Property="SelectedValue" Value="{Binding Path=Kraj}"/>

                                </Style>
                            </DataGridComboBoxColumn.EditingElementStyle>
                        </DataGridComboBoxColumn>