For conditional sorting I use a formula like this:

=IIF(Parameters.SortBy.Value = 1, Fields.id,
 IIF(Parameters.SortBy.Value = 2, Fields.name, Fields.value))

This works perfect.

Now I would like to do the same with the sortings direction! Something like:

=IIF(Parameters.SortOrder.Value = NULL, ASC, IIF(Parameters.SortOrder.Value >= 0, ASC, DESC))

Sadly, the Direction-Field/Dropdown does not support formulas.