WPF Expander - Only one expander to be expanded at any time

Question

In a WPF list view I create few WPF expanders which inside each expander I have few items. Now I want to only one of the expanders to be expanded each time...meaning all other expanders to be collopsed if one is expanded. Can you please help? Please note that the expanders are created by ItemTemplate !

XMAL :

<UserControl x:Class="DataRetrieval.Views.ParametersView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                 xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
                 xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
                 mc:Ignorable="d" 
                  xmlns:local="clr-namespace:DataRetrieval.Views"

                  d:DesignWidth="400"  Height=" 600" Background="White">

            <UserControl.Resources>
                <DataTemplate x:Key="StringDataTemplate">

                    <StackPanel Margin="5" >
                            <TextBlock Text="{Binding Name}" />
                        <TextBox Text="{Binding SelectedValue, UpdateSourceTrigger=PropertyChanged}" Width="290" />
                    </StackPanel>

                </DataTemplate>
                <DataTemplate x:Key="DateDataTemplate">

                    <StackPanel Margin="5" >
                            <ComboBox  SelectedIndex="{Binding SelectedValue, UpdateSourceTrigger=PropertyChanged}" Text="{Binding Name}"  Width="290" ItemsSource="{Binding UserItems}"/>
                        <DatePicker SelectedDate="{Binding multitype.datetime}" Width="200"/>

                    </StackPanel>

                </DataTemplate>


                <local:ParamControlTemplateSelector x:Key="myParamTemplateSelector" />
            </UserControl.Resources>
        <Border BorderBrush="LightGray" BorderThickness="1,1,1,1" CornerRadius="8,8,8,8" Margin="20"  Background="#FFF3F3F3">
            <Grid Margin="5">
                <ScrollViewer VerticalScrollBarVisibility="Auto">
                    <ListView x:Name="myListView1" ItemsSource="{Binding Qtables,  Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" SelectedIndex="{Binding SelectedIndex}">

                        <ListView.ItemTemplate>
                            <DataTemplate>
                                <Expander Header="{Binding Name}"  Width="320" IsExpanded="{Binding IsExpanded}" >
                                        <StackPanel   Height="600">
                                            <TextBlock Text="{Binding Name}" />
                                            <ListView x:Name="myListView" ItemsSource="{Binding Params,  Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" ItemTemplateSelector="{StaticResource myParamTemplateSelector}" SelectedIndex="{Binding CurrentUser, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
                                            </ListView>
                                        </StackPanel>

                                    </Expander>

                            </DataTemplate>
                    </ListView.ItemTemplate>
                   </ListView>
                </ScrollViewer>
            </Grid>
        </Border>
    </UserControl>

ViewModel

namespace DataRetrieval.ViewModel
{
    class ParametersViewModel:BindableBase
    {
        public ParametersViewModel()
        {

            AParams = new WhereParams();
            Qtables = new QDatatables();
            for (int j = 0; j < 5;j++ )
            {


                for (int i = 0; i < 10; ++i)
                {
                    int[] numbers;
                    numbers = new int[3] { 1, 2, 3 };
                    var parameter = new WhereParam { ID = i, Name = "Name " + i.ToString() };

                    if (i == 2 || i == 4)
                    {
                        parameter.Type = ParamTypeEnum.datetimeType;
                    }
                    AParams.Add(parameter);
                }
                var qtable = new QDatatable {  ID=j, Name = j.ToString() + "QTable",  Params = AParams};
                Qtables.Add(qtable);
            }
        }
        private WhereParam _parameter;
        public WhereParam Parameter
        {
            get { return _parameter; }
            set
            {
                SetProperty(ref _parameter, value);
                }
        }
        private WhereParams _paramas;
        public WhereParams AParams
        {
            get { return _paramas; }
            set { SetProperty(ref _paramas, value); }
        }
        private QDatatables _qtables;
        public QDatatables Qtables
        {
            get { return _qtables; }
            set
            {
                SetProperty(ref _qtables, value);

            }
        }




    }
}

Answer 1

This could be done by changing the Model to handle the IsExpanded

Model for QTables:

 public class QDatatables : BindableBase
    {
        public QDatatables()
        {
            List.CollectionChanged += List_CollectionChanged;
        }

        void List_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
        {            
            foreach (var item in e.NewItems)
            {
                var test = item as QDatatable;
                test.PropertyChanged += test_PropertyChanged;
            }            
        }

        void test_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
        {
            if (e.PropertyName == "IsExpanded")
            {
                var cur = sender as QDatatable;
                if (cur.IsExpanded == true)
                {
                    foreach (var item in List)
                    {
                        if (item.Name != cur.Name && item.IsExpanded == true)
                        {
                            item.IsExpanded = false;
                        }
                    }    
                }

            }

        }

        private ObservableCollection<QDatatable> _list;
        public ObservableCollection<QDatatable> List
        {
            get { return _list ?? (_list=new ObservableCollection<QDatatable>()); }
            set { SetProperty(ref _list, value); }
        }



    }