I have problem when I draw a string in XNA 4.0 3D.I known problem is `spriteBatch.Begin()`. But I don't know how to solve it.

```
protected override void Draw(GameTime gameTime)
{
  GraphicsDevice.Clear(Color.DeepSkyBlue);
  //Draw string 
  spriteBatch.Begin();
  spriteBatch.DrawString(fontArial, "Demotesting", new Vector2(100, 100), Color.Red);
  spriteBatch.End();
  //Draw Models Ship
  ship.Draw();

  base.Draw(gameTime);
}

```

Before draw string:
<http://nq1.upanh.com/b4.s32.d1/6c6ce19bded8d054341ce45e17426c51_49358001.before.png>

After draw string:
<http://nq2.upanh.com/b6.s30.d2/9ff7c3c009215348b06a53c5a067d282_49358002.after.png>