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 { d.CompanyId, d.CompanyName, d.Place };
              listBox1.DataContext = users;
              dataGrid1.DataContext = users;
             //   foreach (String c in customers)
             //  {
             //      MessageBox.Show(c.ToString());
             //  }
        }
      }
When try to double clikc on the datagrid   it through s  a  error    with 
Caption " Invalid Operation Execption was unhandled "  and 
Message " A TwoWay or OneWayToSource binding cannot work on the read-only property 'CompanyId' of type '<f__AnonymousType0`3[System.Int32,System.String,System.String]'. 
whats wrong here 
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>
</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();
    }