2-Way databinding with Entity Framework and WPF DataGrid , is Possible?

i am working on POS application using SQL CE , WPF , Entity framework 3.5sp2 and iam trying to use data grid as my Order Entry Control for User to enter Products Order . Iam plannning to bind this to enitiy frmae work model , abd looking for 2 way updating ?

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        using (MasterEntities nwEntities = new MasterEntities())
        {
          var users = from d in nwEntities.Companies
        select new CompanyRowModel{ CompanyId = d.CompanyId, CompanyName       d.CompanyName, Place = d.Place }

              listBox1.DataContext = users;
              dataGrid1.DataContext = users;
        }           
      }

      public class CompanyRowModel
      {
        public int CompanyId { get; set; }
        public string CompanyName { get; set; }
        public string Place{ get; set; }
      }

and my xaml coding goes like this

   <Grid>
     <ListBox Name="listBox1" ItemsSource="{Binding}"  />
    <Button Content="Show "  Name="button1" Click="button1_Click"  />

    <DataGrid AutoGenerateColumns="False" Name="dataGrid1" ItemsSource="{Binding}" >
      <DataGrid.Columns>
          <DataGridTextColumn Header=" ID"     Binding="{Binding CompanyId}"/>
          <DataGridTextColumn Header="Company Name"  Binding="{Binding CompanyName}"/>
          <DataGridTextColumn Header="Place"    Binding="{Binding Place}" />
        </DataGrid.Columns>
    </DataGrid>
    <Button Content="Save"  Name="button2" VerticalAlignment="Bottom" Click="button2_Click" />
</Grid>

EDITED :

i made the changes shown by @vorrtex, But, then i added another button to save the chages and in button click event i added follwing code , butit showing Updating error

  private void button2_Click(object sender, RoutedEventArgs e)
    {
         nwEntities.SaveChanges();
    }