в поле зрения
<DataGrid ItemSource="{Binding MyItems}"
SelectedItem = "{Binding MyCurrentItem}"
>
в ВМ
private Myobject myCurrentItem;
public Myobject MyCurrentItem
{
get{ return myCurrentItem; }
set{
if (myCurrentItem!=value)
{
myCurrentItem=value;
DoMyStuff();
}
}
}