A field has a Visibility flag which can be set declaratively (XAML) or via code. I assume, you want to do this in code - here's a dummy snippet that shows/hides the first column of a given grid:

      Field field = myGrid.FieldLayouts[0].Fields[0];
      if (field.Visibility == Visibility.Visible)
      {
        field.Visibility = Visibility.Collapsed;
      }
      else
      {
        field.Visibility = Visibility.Visible;
      }

hth