title: How to set SortDirection of a WPF datagrid as Ascending on datagrid initialization
body: <p>I have a simple datagrid which can be sorted by clicking the column header.
  When I open the window, datagrid is not sorted. Then, when I click, arrow appears and it's sorted asc, click again - sorted desc etc. very simple. </p>
  
  <p>What I need to do, is to open window with already sorted datagrid. So arrows (that shows which direction datagrid is sorted) should be always visible. I have to have my datagrid sorted all the time. 
  How can I do that? I prefer to do that in xaml,  but any solution will be great.</p>
  
  <p>BTW. App in .NET4 </p>