Shooting with rotation

Do anyone know how to make bullets shoot in the direction the player is heading or where the mouse is?
Like in a top down shooter!


Vector2 mouse;
Vector2 player;

Vector2 dir = Vector2.Normalize(mouse-player);

Thanks! But do I just dir.Y += 2; or???

bulletposition += dir*(speedofthebullet)

Oh, thank you so much!