重构XNA中的映射加载开关语句

我有一个switch语句，它接受一个元组，并根据元组的第二个值选择要进入哪一组嵌套switch语句。用这种方式一切都运行得很好，但是因为我需要在中心地图周围加载4个地图，以便每次平滑过渡，所以switch语句最终占用了比必要更多的空间。我正在重构一个方法，它现在只是加载并绘制基本精灵。我遇到了一些问题，内容管理器在加载精灵时收到空引用异常，不知道如何正确地将内容传递给Load方法。

下面是我在Draw中的Switch语句的缩写:

GraphicsDevice.Clear(Color.CornflowerBlue);
spriteBatch.Begin(SpriteSortMode.FrontToBack, BlendState.AlphaBlend);
Map.FindLocation(Map.LocationXY, ZoneDecider);
switch (Map.TupleHolder.Item1)
{
   case 0:
   {
      switch (Map.TupleHolder.Item2)
      {
         case 0:
            if (LoadNextMap)
            {
               if (Right)
               {
                  backgroundCenter.LoadContent(this.Content,"BackgroundBottom");
                  backgroundCenter.position = new Vector2(0, 0);
               }
               else if (Left)
               {
                  backgroundCenter.LoadContent(this.Content, "BackgroundBottom");
                  backgroundCenter.position = new Vector2(0, 0);
               }
               else if (Top)
               {
                  backgroundCenter.LoadContent(this.Content, "BackgroundBottomRight");
                  backgroundCenter.position = new Vector2(0, 0);
               }
               else if(Bottom)
               {
                  backgroundCenter.LoadContent(this.Content, "BackgroundRight");
                  backgroundCenter.position = new Vector2(0, 0);
               }
               backgroundWest.LoadContent(this.Content, "BackgroundBottom");
               backgroundWest.position = new Vector2(westTransition, 0);
               backgroundEast.LoadContent(this.Content, "BackgroundBottomRight");
               backgroundEast.position = new Vector2(eastTransition, 0);
               backgroundNorth.LoadContent(this.Content, "BackgroundMid");
               backgroundNorth.position = new Vector2(0, northTransition);
               backgroundSouth.LoadContent(this.Content, "BackgroundBottomRight");
               backgroundSouth.position = new Vector2(0, southTransition);
               LoadNextMap = false;
            }
            //new SpriteBatch(graphicsDevice)
            backgroundCenter.Draw(this.spriteBatch);
            //Drawbackground.drawBackground(backgroundWest, backgroundEast,
            // backgroundNorth, backgroundSouth);
            backgroundWest.Draw(this.spriteBatch);
            backgroundEast.Draw(this.spriteBatch);
            backgroundNorth.Draw(this.spriteBatch);
            backgroundSouth.Draw(this.spriteBatch);
            break;

这并不理想，所以为了开始重构，我将if语句的部分移到一个新方法中。

新方法

public class DrawNextBackground
{
    SpriteBatch spriteBatch;
    ContentManager theContentManager;
    public void drawBackground(Background backgroundWest,
        Background backgroundEast, Background backgroundNorth, Background backgroundSouth)
    {
        float eastTransition = 1068;
        float westTransition = -1068;
        float northTransition = -936;
        float southTransition = 936;
        backgroundWest.LoadContent(this.theContentManager, "BackgroundBottom");
        backgroundWest.position = new Vector2(westTransition, 0);
        backgroundEast.LoadContent(this.theContentManager, "BackgroundBottomRight");
        backgroundEast.position = new Vector2(eastTransition, 0);
        backgroundNorth.LoadContent(this.theContentManager, "BackgroundMid");
        backgroundNorth.position = new Vector2(0, northTransition);
        backgroundSouth.LoadContent(this.theContentManager, "BackgroundBottomRight");
        backgroundSouth.position = new Vector2(0, southTransition);
        backgroundWest.Draw(this.spriteBatch);
        backgroundEast.Draw(this.spriteBatch);
        backgroundNorth.Draw(this.spriteBatch);
        backgroundSouth.Draw(this.spriteBatch);
    }
}

Load Method:

    public void LoadContent(ContentManager theContentManager, string theAssetName)
    {
        SpriteSize = theContentManager.Load<Texture2D>(theAssetName);
    }

如何让Load方法注意到每个对象都有内容?