Access Checkbox inside list box in C# in Windows Phone

Question

Hello

I am developing a windows phone application. I have created check box inside list box in XAML. Following is the XAML code

 <ListBox Name="lstcontacts" ItemsSource="{Binding}" Margin="10,52,10,113" SelectionMode="Multiple" Foreground="#FF333333" >

                <ListBox.ItemTemplate>

                    

                    <DataTemplate>

                        <StackPanel Orientation="Horizontal">

                            <CheckBox Name="contactChk" IsChecked="true" Foreground="Black" Background="Black" BorderBrush="Black" />

                            <TextBlock Name="txtResults" Text="{Binding Path=DisplayName, Mode=OneWay}"  />

                        </StackPanel>

                    </DataTemplate>

                </ListBox.ItemTemplate>

            </ListBox>

I want to access checkBox name contactChk via C# and want to access check box value in C#. but i am unable to access Check box in C#. Can anybody please tell me how can i do this.