MonoGame XNA Helloworld with a Texture2D

我在使用Texture2D类时有一些麻烦。我很确定这是一个相当简单的问题。我得到以下错误:

Error   1   Expected class, delegate, enum, interface, or struct    D:'_Projects'MonoGameWindowsApplication1'MonoGameWindowsApplication1'Game1.cs   14  13  MonoGameWindowsApplication1

我似乎没有引用Texture2D类，但我不知道为什么我不这样做。如果有任何帮助就太好了。

#region Using Statements
using System;
using System.Collections.Generic;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Storage;
using Microsoft.Xna.Framework.GamerServices;
#endregion
namespace MonoGameWindowsApplication1
{
    private Texture2D background; // <---- This is where I get the above error.
    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;
        public Game1()
            : base()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";

        }
        /// <summary>
        /// Allows the game to perform any initialization it needs to before starting to run.
        /// This is where it can query for any required services and load any non-graphic
        /// related content.  Calling base.Initialize will enumerate through any components
        /// and initialize them as well.
        /// </summary>
        protected override void Initialize()
        {
            // TODO: Add your initialization logic here
            base.Initialize();
        }
        /// <summary>
        /// LoadContent will be called once per game and is the place to load
        /// all of your content.
        /// </summary>
        protected override void LoadContent()
        {
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);
            // TODO: use this.Content to load your game content here
        }
        /// <summary>
        /// UnloadContent will be called once per game and is the place to unload
        /// all content.
        /// </summary>
        protected override void UnloadContent()
        {
            // TODO: Unload any non ContentManager content here
        }
        /// <summary>
        /// Allows the game to run logic such as updating the world,
        /// checking for collisions, gathering input, and playing audio.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Update(GameTime gameTime)
        {
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed || Keyboard.GetState().IsKeyDown(Keys.Escape))
                Exit();
            // TODO: Add your update logic here
            base.Update(gameTime);
        }
        /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);
            // TODO: Add your drawing code here
            base.Draw(gameTime);
        }
    }
}