To SL3, currently we see that the best way is to:
http://www.sharpgis.net/post/2009/09/17/Add-MouseWheel-scrolling-to-Silverlights-DataGrid.aspx
In the datagrid header plus scrollviewer will also scroll.
Reproduced in: https: //www.cnblogs.com/belaliu/archive/2010/03/18/1688844.html