You need a Tuple
of arity 2:
public SortedList<Tuple<string,string>,double> mySortedList ;
Though you'll probably have to provide it with a custom comparer, something like:
class My2TupleComparer : IComparer<Tuple<string,string>
{
public int Compare(Tuple<string,string> x, Tuple<string,string> y )
{
int cc ;
if ( x == null && y == null ) cc = 0 ;
else if ( x == null && y != null ) cc = -1 ;
else if ( x != null && y == null ) cc = +1 ;
else /* ( x != null && y != null ) */
{
cc = string.Compare(x.Item1 , y.Item1 , StringComparison.OrdinalIgnoreCase ) ;
if ( cc == 0 )
{
cc = String.Compare( x.Item2 , y.Item2 , StringComparison.OrdinalIgnoreCase ) ;
}
}
return cc ;
}
}