NullReferenceException in XNA with C#

我正在尝试为带有XNA和C#的Windows制作一个简单的3D游戏。我正在尝试创建视图矩阵，正如每个教程甚至 MSDN 所建议的那样，但我收到 NullReferenceException 错误。

错误显示：对象引用未设置为对象的实例。它指向投影矩阵的定义：

projectionMatrix = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, device.Viewport.AspectRatio, 1.0f, 300.0f);

这是我的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;
namespace Series3D1
{
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        Effect effect;
        VertexPositionColor[] vertices;
        Matrix viewMatrix;
        Matrix projectionMatrix;
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;
        GraphicsDevice device;
        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
        }
        protected override void Initialize()
        {
            graphics.PreferredBackBufferWidth = 500;
            graphics.PreferredBackBufferHeight = 500;
            graphics.IsFullScreen = false;
            graphics.ApplyChanges();
            Window.Title = "Riemer's XNA Tutorials -- Series 1";
            base.Initialize();
        }
        protected override void LoadContent()
        {
            spriteBatch = new SpriteBatch(GraphicsDevice);
            SetUpCamera();
            effect = Content.Load<Effect>("effects");
            SetUpVerticies();
            device = graphics.GraphicsDevice;
        }
        protected override void UnloadContent()
        {
        }
        protected override void Update(GameTime gameTime)
        {
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                this.Exit();
            base.Update(gameTime);
        }
        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);
            effect.CurrentTechnique = effect.Techniques["ColoredNoShading"];
            effect.Parameters["xView"].SetValue(viewMatrix);
            effect.Parameters["xProjection"].SetValue(projectionMatrix);
            effect.Parameters["xWorld"].SetValue(Matrix.Identity);
            foreach (EffectPass pass in effect.CurrentTechnique.Passes)
            {
                pass.Apply();
            }
            device.DrawUserPrimitives(PrimitiveType.TriangleList, vertices, 0, 1, VertexPositionColor.VertexDeclaration);
            base.Draw(gameTime);
        }
        private void SetUpVerticies()
        {
            vertices = new VertexPositionColor[3];
            vertices[0].Position = new Vector3(0f, 0f, 0f);
            vertices[0].Color = Color.Red;
            vertices[1].Position = new Vector3(10f, 10f, 0f);
            vertices[1].Color = Color.Green;
            vertices[2].Position = new Vector3(10f, 0f, -5f);
            vertices[2].Color = Color.Yellow;
        }
        private void SetUpCamera()
        {
            viewMatrix = Matrix.CreateLookAt(new Vector3(0, 0, 50), new Vector3(0, 0, 0), new Vector3(0, 1, 0));
            projectionMatrix = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, device.Viewport.AspectRatio, 1.0f, 300.0f);
        }
    }
}

protected override void LoadContent()
{
    spriteBatch = new SpriteBatch(GraphicsDevice);
    SetUpCamera();
    effect = Content.Load<Effect>("effects");
    SetUpVerticies();
    device = graphics.GraphicsDevice;
}

protected override void LoadContent()
{
    device = graphics.GraphicsDevice;
    spriteBatch = new SpriteBatch(GraphicsDevice);
    SetUpCamera();
    effect = Content.Load<Effect>("effects");
    SetUpVerticies();
}