Setting the door density?

How to set the door density? I need to make the players can walk through the doors.

Code:

void OnDoorOpened(Door door, BasePlayer player)
{     
            Rigidbody Body = door.GetComponent<Rigidbody>(); // #1 NULL            Rigidbody BodyComponent = door.gameObject.AddComponent<Rigidbody>(); // #2 NULL            /*BodyComponent.SetDensity(0f);
            BodyComponent.detectCollisions = false;*/
}