title: I want data in the rest of wpf DataGrid to be read only and only new row should be editable
body: <p>I have managed to get <code>DataGrid</code> to show new row for adding new item.
  Problem i face now is i want data in the rest of wpf <code>DataGrid</code> to be read only and only new row should be editable.</p>
  
  <p>Currently this is how my <code>DataGrid</code> looks.</p>
  
  <pre><code>&lt;DataGrid AutoGenerateColumns="False" Name="DataGridTest" CanUserAddRows="True" Grid.Row="2" ItemsSource="{Binding TestBinding}" &gt;
      &lt;DataGrid.Columns&gt;        
          &lt;DataGridTextColumn Header="Line" IsReadOnly="True" Binding="{Binding Path=Test1}" Width="50"&gt;&lt;/DataGridTextColumn&gt;
          &lt;DataGridTextColumn Header="Account" IsReadOnly="True"  Binding="{Binding Path=Test2}" Width="130"&gt;&lt;/DataGridTextColumn&gt;               
      &lt;/DataGrid.Columns&gt;
  &lt;/DataGrid&gt;
  </code></pre>
  
  <p>But since I have kept the columns read only, a new row also adds as read only which is what I don't want.</p>