Which of the following statements is incorrect for a current-carrying solenoid?

• A
  The magnetic field at all points inside the solenoid is uniform.
• B
  It acts as a magnet when a soft iron core is placed inside it to produce a strong magnetic field.
• C
  The pattern of its magnetic field lines is different from that of a bar magnet.
• D
  Reversing the direction of the current in the solenoid reverses the positions of its $N$ and $S$ poles.