problem direction

Unity Engine
1

Hello,
problems of rotation and addforce (direction),
I would like to rotation by right analog stick, and by the y-axis of left analog stick translate (with addforce) only in this direction (of that rotation).
Thank you and good day.
Cordially.

2

this.rigidBody.AddForce(this.transform.forward);

3

Hello,
Thank you infinitely,
But the problem is that vector3.forward solves the problem partially.
for exemple :
when the direction is 45 degree or 90 degree or 135 or 115 or so on etc , the player goes in this direction.
(a direction in 360 degrees around the player)
Thank you and good day.

4

Sorry,
Problem solved .