How to get column values of selected columns in datagrid wpf

Question

I have a Listbox in which I have added two controls i.e a Checkbox and a Datagrid side by side as a Listboxitem. I have done it in a following manner:

In Code behind: listBox1.items.Add(dt)

here dt is the table name.

In Xaml:

<ListBox Grid.Row="0" AlternationCount="2" MinHeight="305" HorizontalAlignment="Stretch" Name="listBox1" VerticalAlignment="Stretch" MinWidth="537" >
  <ListBox.ItemTemplate>
    <DataTemplate>
      <StackPanel Name="stkPanel" MinHeight="80" MinWidth="500" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
        <Grid>
          <Grid.ColumnDefinitions> 
              <ColumnDefinition Width="40"/>
              <ColumnDefinition Width="Auto"/>
         </Grid.ColumnDefinitions>
         <DataGrid Grid.Column="1" AutoGenerateColumns="True" MinHeight="75" HorizontalAlignment="Center" Name="dataGrid1" VerticalAlignment="Stretch" MinWidth="470" MaxWidth="900" ItemsSource="{Binding}" IsReadOnly="True" Background="#E6BAB7B7">
            <DataGrid.ColumnHeaderStyle>
                <Style TargetType="DataGridColumnHeader">
                   <Setter Property="ContentTemplate">
                        <Setter.Value>
                            <DataTemplate>
                              <CheckBox Name="colCheckBox" IsChecked="{Binding IsChecked, ElementName=IsDone, Mode=OneWay}" Content="{Binding}"/>
                            </DataTemplate>
                        </Setter.Value>
                   </Setter>
               </Style>
            </DataGrid.ColumnHeaderStyle>
         </DataGrid> 
         <CheckBox Grid.Column="0" Height="35" Width="25" Name="IsDone" HorizontalAlignment="Right" VerticalAlignment="Center" Checked="IsDone_Checked" />
       </Grid>
    </StackPanel>
 </DataTemplate>
 </ListBox.ItemTemplate> 
</ListBox> 

Suppose for first listboxitem, there is "IsDone" checkbox and a datagrid. If I select "IsDone" check box (listbox item) all the datagrid column header check box is selected.Now, I can uncheck some of the datagrid coulmn header check boxes.What I want is to get values of the entire column only whose columnheader check box is checked and bind those values to a datatable.Similarly repeat the above process for other listbox item.Can you please suggest me how to do that in wpf?