How to get the value associated with checkbox present in data template of listview?

I am trying to get the values/contents of the "selected" check-boxes so that i can use it to get data from sqlite database in the back-end . But I am unable to get the value of the checkbox from the listview.

This is the listview -

<ListView x:Name="listview" Background="Azure" SelectionMode="Multiple"
         ItemsSource="{Binding Strings}" RenderTransformOrigin="0.5,0.5" Width="343">
            <ListView.ItemTemplate>
                <DataTemplate x:Name="datatemplate">
                    <CheckBox x:Name="CheckBoxZone" IsChecked="{Binding RelativeSource={RelativeSource AncestorType=ListViewItem},Path=IsSelected}"
                              Content="{Binding que_text}" Margin="0,5,0,0"/>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
        <Button  Style="{StaticResource ResourceKey=button_style }" x:Name="addToSurvey" Content="Add" Click="AddToSurvey_Click" />

this is the function-

private void AddToSurvey_Click(object sender, RoutedEventArgs e)
        {

            //foreach (var item in listview.SelectedItems)
            for (int i=0;i< listview.SelectedItems.Count;i++)
            {
                string que = listview.Items[i].ToString(); //did not work

            }

        }

this is the Questions class -

 public class Questions
    {
        public int que_id { get; set; }
        public string que_text { get; set; }
    }

the checkbox hold the que_text value which i need to retrieve for getting the que_id from the database. Please help me out !