How to properly use conditions in C#?

Question

C++ / C#

I am writing a test case in Unity, here is a piece

public class MovePlayer : MonoBehaviour{
  public Transform player;
  void OnMouseDrag(){
    Vector3 mousePos = Camera.main.ScreenToWorldPoint (Input.mousePosition);
    mousePos.x = mousePos.x > 3f ? 3f : mousePos.x;
    /*--------*/
    if (mousePos.x>3f) mousePos.x=3f; else mousePos.x;
               /*--------*/
    player.position = new Vector2 (mousePos.x, player.position.y);
    }
  }

mousePos.x = mousePos.x > 3f ? 3f : mousePos.x;

works

if (mousePos.x>3f) mousePos.x=3f; else mousePos.x;

does not work,
although in theory these conditions are identical ...
Tell me what's wrong, just switched from PHP, and the syntax seems to be the same ...

Answer 1

And why are there generally yes the same conditions? The second condition does not make sense after the first, where everything has already been checked.