Get a particular cell value in the WPF datagrid row when a different cell is selected

Hi, using Visual C# 2010 Express, in WPF datagrid I have SelectionUnit="CellOrRowHeader"
The datagrid is populated by a datatable from a database query
Now,

1) when the user selects any cell in the datagrid I want to read certain cells on the same row as the selected cell
Let's say, if cell [row=5, col=2] is selected I want to now get values in cell [row=5, col=1]
How can I do this?

2) When I select any Cell, why is the grid SelectedIndex always '-1' ?
In traditional winforms datagridview, selecting any cell would make the corresponding row the Current Row
How to make the row of a selected cell the Current Row in WPF?
I don't want to change SelectionUnit="CellOrRowHeader" because I want to let users select specific cell so they can copy the contents of that cell only
Also, is there an easy way to show the current row indicator in WPF datagrid (like the triangle in row header in winforms datagridview)?


Thanks,
-sri

sri