how to get the value of checkbox which is inside the combo box WPF?

i have a combobox and the checkbox is present inside the combobox.i want the value of the multi selection checkbox.

my code-

    <ComboBox Name="LocationFilterComboBox" Width="100" SelectedItem="{Binding LocationValue}"  >
   <ComboBox.ItemTemplate >
 <DataTemplate>
<StackPanel Orientation="Horizontal" >
 <CheckBox Content="{Binding LocationValue}"  IsChecked="{Binding ElementName=all, Path=IsChecked, Mode=TwoWay}" Width="120" />
 </StackPanel>
</DataTemplate>
 </ComboBox.ItemTemplate>
</ComboBox>