How to control visibility of DataGridTextColumn

Question

I named two columns like this

<data:DataGridTextColumn Width="60*" Header="Status" 
 Binding="{Binding F_status}" x:Name="f_status" />

<data:DataGridTextColumn Width="30*" Header="Level" 
 Binding="{Binding F_level}" x:Name="f_level" />

and I want to show these two columns dynamically...

when I am coding in CS file like this

if ("1".Equals(board_folder_type))
{
  f_status.Visibility = Visibility.Visible;
  f_level.Visibility = Visibility.Visible;
}
else
{
  f_status.Visibility = Visibility.Collapsed;
  f_level.Visibility = Visibility.Collapsed;
}

it gives me NullReferenceException...

please help me :(

ps. forgive me that my English is bad...

Answer 1

You should do like this,

Datagrid.Columns[YourColumnIndex].Visibility = Visibility.Visible;

If you column "f_status" is the first column of your datagrid, do this way,

if ("1".Equals(board_folder_type))
{
  Datagrid.Columns[0].Visibility.Visibility = Visibility.Visible;

}