public partial class App : Application
{                                                                                                                                                                                                                                                                  EventManager.RegisterClassHandler(typeof(TextBox), TextBox.KeyDownEvent, new KeyEventHandler(TextBox_KeyDown));
     ...
} 
 private void TextBox_KeyDown(object sender, KeyEventArgs e)
   {
         if (e.Key != Key.Enter)
             return;
         var focusedElement = Keyboard.FocusedElement as TextBox;
          focusedElement.MoveFocus(new TraversalRequest(FocusNavigationDirection .Next));
   }

public class CommonDataGrid : DataGrid
{
        protected override void OnPreviewKeyDown(KeyEventArgs e)
        {
            base.OnPreviewKeyDown(e);
            if (e.Key != Key.Enter || Keyboard.PrimaryDevice.ActiveSource == null) return;
            this.CommitEdit();
            var args = new KeyEventArgs
                (Keyboard.PrimaryDevice,
                Keyboard.PrimaryDevice.ActiveSource, 0, Key.Tab) { RoutedEvent = Keyboard.KeyDownEvent };
            InputManager.Current.ProcessInput(args);
        }
}