Alternative To Dynamic Sql?

I have a procedure that take several paramters and depending of what
values is submitted or not, the procedures shall return different
number of rows. But to simplyfy this my example use just one
parameter, for example Idnr.

If this id is submitted then I will return only the posts with this
idnr, but if this is not submitted, I will return all posts in table.
As I can see I have two options
1. IF @lcIdNr IS NOT NULL
SELECT *
FROM table
WHERE idnr = @lcIdNr
ELSE
SELECT *
FROM table

2. Use dynamic SQL.

The first example can work with just one parameter but with a couple
of different input paramters this could be difficult, anyway this is
not a good solution. The second example works fine but as I understand
dynamic sql is not good from the optimizing point of view. So, I don't
want to use either of theese options, so I wonder If there i a way to
work around this with for example a case clause?

Regards
Jenny