Time for action – updating and drawing the StarField

1. Add the Update() and Draw() methods to the StarField class:

   Public Sub Update(gameTime As GameTime)
       For Each star As Sprite in Stars
           star.Update(gameTime)
           If (star.Location.Y > screenHeight) Then
               star.Location = new Vector2(
                   CSng(rand.Next(0, screenWidth)), 0)
           End If
       Next
   End Sub
   
   Public Sub Draw(spriteBatch As SpriteBatch)
       For Each star As Sprite in stars
           star.Draw(spriteBatch)
       Next
   End Sub

What just happened?

When the StarField needs to be updated, a For Each loop processes each item in the stars list, running the sprite's Update() method. The method then checks the star's Location property's Y component to determine if the star has moved off the bottom of the screen. If it has, the star is assigned a new Location with a random X component and a Y component of zero, placing the star at a random location along the top of the screen.

The StarField.Draw() method...