title: Get column index by Column header in WPF DataGrid
body: <p>How to get the <code>Column</code> index or <code>Column.DisplayIndex</code> from its <code>Column Header</code> in <code>WPF</code> <code>DataGrid</code>?</p>
  
  <p>I know the <code>Column Header</code>, want to get <code>column index</code>.</p>