XNA项目中的菜单加载错误，以加载3D菜单

Question

我正在尝试在XNA中进行3D菜单，但我收到的错误如下 “当前上下文中不存在名称'item_OnTap'。”我是XNA编程的新手。请提前感谢。

//ModelMenuGame.cs


   public class ModelMenuGame : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;

        SpriteFont font;
        Model menuItemModel;
        Vector3 cameraPosition;

        Matrix view;
        Matrix projection;
        List<ModelMenuItem> Menu;
        int TotalMenuItems = 4;

        Rectangle LeftRegion;
        Rectangle RightRegion;

        int currentIndex = 0;
        public event EventHandler OnTap;


        public ModelMenuGame()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";

            TargetElapsedTime = TimeSpan.FromTicks(333333);

            // Extend battery life under lock.
            InactiveSleepTime = TimeSpan.FromSeconds(1);
        }


        protected override void Initialize()
        {
            // TODO: Add your initialization logic here
            cameraPosition = new Vector3(-40, 10, 40);
            view = Matrix.CreateLookAt(cameraPosition, Vector3.Zero, Vector3.Up);
            projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, GraphicsDevice.Viewport.AspectRatio, 1.0f, 1000.0f);
            Menu = new List<ModelMenuItem>();

            LeftRegion = new Rectangle(0, 0, GraphicsDevice.Viewport.Width / 2, GraphicsDevice.Viewport.Height);
            RightRegion = new Rectangle(GraphicsDevice.Viewport.Width / 2, 0, GraphicsDevice.Viewport.Width / 2, GraphicsDevice.Viewport.Height);


            OnTap = new EventHandler(item_OnTap);
            currentIndex = currentIndex % TotalMenuItems;
            if (currentIndex < 0)
            {
                currentIndex = TotalMenuItems - 1;
            }
            else if(currentIndex > TotalMenuItems - 1)
                {
                    currentIndex = 0;
                }
            foreach (ModelMenuItem item in Menu)
            {
                if (item.Index == currentIndex)
                {
                    item.Selected = true;
                }
                else
                {
                    item.Selected = false;
                }
            }


            menuItemModel = Content.Load<Model>("ModelMenuItem3D");

            font = Content.Load<SpriteFont>("gameFont");

            for (int i = 0; i < TotalMenuItems; i++ )
            {
                int X = -20;
                ModelMenuItem item =  new ModelMenuItem(this, menuItemModel, view, projection);

                item.Translation = new Vector3(X + (i * 20), 0, 0);
                item.Index = i;
                Menu.Add(item);
            }
            Menu[0].Selected = true;


            base.Initialize();
        }

这是代码     //ModelMenuItem.cs     public class ModelMenuItem：Microsoft.Xna.Framework.GameComponent         {

        Model modelItem;

        public Vector3 Translation;

        public Matrix View;

        public Matrix Projection;

        public int Index;

        public bool Selected;

        public int Offset;


        public ModelMenuItem(Game game, Model model, Matrix view, Matrix projection)
            : base(game)
        {
            // TODO: Construct any child components here
            modelItem = model;
            View = view;
            Projection = projection;
            Offset = 5;
         }

        public void Draw()
        {
            Matrix[] modelTransforms = new Matrix[modelItem.Bones.Count];
            modelItem.CopyAbsoluteBoneTransformsTo(modelTransforms);
            foreach (ModelMesh mesh in modelItem.Meshes)
            {
            foreach(BasicEffect effect in mesh.Effects)
            {
                effect.EnableDefaultLighting();
                effect.AmbientLightColor = Color.White.ToVector3();

                if (Selected)
                {
                    effect.World = modelTransforms[mesh.ParentBone.Index] * Matrix.CreateTranslation(Translation + new Vector3(0, 0, Offset));
                }
                else
                {
                    effect.World = modelTransforms[mesh.ParentBone.Index] * Matrix.CreateTranslation(Translation);
                }
                effect.View = View;
                effect.Projection = Projection;
            }
            mesh.Draw();
            }

        }