Cant use DataGrid.HitTestInfo

Hi,

I´m trying to know where the user has clicked in a datagrid (header, row,
footer).
I have looked throw the internet, and found this good article.
http://samples.gotdotnet.com/quickst...atagridsorting
..aspx

but I can´t use it. It seems not to recognice the DataGrid.HitTestInfo
class.
I have try to add this using clause too (using
System.Windows.Forms.DataGrid, but it doesnt recognice.

What am I doing wrong or missing?
Is there any other way to know if the user has clicked in a row or in a
header?

Thanks,
--
Ibai Peña