在C#中的键上绘制不同的精灵

im试图用enums在按键上绘制不同的精灵，遵循了我在这个网站上找到的一个例子，但我的代码似乎只呈现Sprite_1。我最初在bools上设置了这个，但这样我也只能加载一个精灵，奇怪的是，尽管它是一个不同的精灵（精灵_2）。我做错了什么？

using System;
using System.Text;
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.Storage;
using Microsoft.Xna.Framework.Media;
namespace WindowsGame3
{
/// <summary>
/// This is the main type for your game
/// </summary>
public class Game1 : Microsoft.Xna.Framework.Game
{
    GraphicsDeviceManager graphics;
    SpriteBatch spriteBatch;
    //Screen Stuff
    const int Screen_Height = 1280;
    const int Screen_Width = 720;
    Rectangle Screen_Bounds;
    //Sprite stuff
    int Player_Size = 60;
    Rectangle Player1;
    Rectangle Player2;
    Rectangle Player3;
    Rectangle Player4;
    public Game1()
    {
        graphics = new GraphicsDeviceManager(this);
        Content.RootDirectory = "Content";
        Screen_Bounds = new Rectangle(0, 0, Screen_Width, Screen_Height);
    }
    /// <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();
    }
    enum Spritestate
    {
        Player_Left,
        Player_Right,
        Player_Up,
        Player_Down
    }
    Spritestate RealTime_Player;
    /// <summary>
    /// LoadContent will be called once per game and is the place to load
    /// all of your content.
    /// </summary>
    /// 
    Texture2D Sprite_1;//Facing Right
    Vector2 Sprite_1Position = new Vector2(100, 100);
    Texture2D Sprite_2;//Facing Left
    Vector2 Sprite_2Position = new Vector2(100, 100);
    Texture2D Sprite_3;//Facing Up
    Vector2 Sprite_3Position = new Vector2(100, 100);
    Texture2D Sprite_4;//Facing Down
    Vector2 Sprite_4Position = new Vector2(100, 100);
    protected override void LoadContent()
    {
        // Create a new SpriteBatch, which can be used to draw textures.
        spriteBatch = new SpriteBatch(GraphicsDevice);
        Sprite_1 = Content.Load<Texture2D>("Tank_Right");
        Sprite_2 = Content.Load<Texture2D>("Tank_Left");
        Sprite_3 = Content.Load<Texture2D>("Tank_Up");
        Sprite_4 = Content.Load<Texture2D>("Tank_Down");
        // 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)
    {
        // Allows the game to exit
        if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
            this.Exit();
        KeyboardState keyboard = Keyboard.GetState();
        if (keyboard.IsKeyDown(Keys.W))
        {
            Spritestate RealTime_Player = Spritestate.Player_Up;
            Sprite_1Position.Y -= 5;
            Sprite_2Position.Y -= 5;
            Sprite_3Position.Y -= 5;
            Sprite_4Position.Y -= 5;
        }
        if (keyboard.IsKeyDown(Keys.A))
        {
            Spritestate RealTime_Player = Spritestate.Player_Right;
            Sprite_1Position.X -= 5;
            Sprite_2Position.X -= 5;
            Sprite_3Position.X -= 5;
            Sprite_4Position.X -= 5;
        }
        if (keyboard.IsKeyDown(Keys.S))
        {
            Spritestate RealTime_Player = Spritestate.Player_Down;
            Sprite_1Position.Y += 5;
            Sprite_2Position.Y += 5;
            Sprite_3Position.Y += 5;
            Sprite_4Position.Y += 5;
        }
        if (keyboard.IsKeyDown(Keys.D))
        {
            Spritestate RealTime_Player = Spritestate.Player_Left;
            Sprite_1Position.X += 5;
            Sprite_2Position.X += 5;
            Sprite_3Position.X += 5;
            Sprite_4Position.X += 5;
        }
        Player1 = new Rectangle((int)Sprite_1Position.X, (int)Sprite_1Position.Y, Player_Size, Player_Size);
        Player2 = new Rectangle((int)Sprite_2Position.X, (int)Sprite_2Position.Y, Player_Size, Player_Size);
        Player3 = new Rectangle((int)Sprite_3Position.X, (int)Sprite_3Position.Y, Player_Size, Player_Size);
        Player4 = new Rectangle((int)Sprite_4Position.X, (int)Sprite_4Position.Y, Player_Size, Player_Size);
        // 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
        spriteBatch.Begin();
        switch (RealTime_Player)
        {
            case Spritestate.Player_Right:
                spriteBatch.Draw(Sprite_1, Player1, Color.White);
                Vector2 Sprite_1Position = new Vector2(100, 100);
                break;
            case Spritestate.Player_Left:
                spriteBatch.Draw(Sprite_2, Player2, Color.White);
                Vector2 Sprite_2Position = new Vector2(100, 100);
            break;
            case Spritestate.Player_Up:
                spriteBatch.Draw(Sprite_3, Player3, Color.White);
                Vector2 Sprite_3Position = new Vector2(100, 100);
            break;
            case Spritestate.Player_Down:
                spriteBatch.Draw(Sprite_4, Player4, Color.White);
                Vector2 Sprite_4Position = new Vector2(100, 100);
            break;
        }
        spriteBatch.End();
        base.Draw(gameTime);
    }
}

}

if (keyboard.IsKeyDown(Keys.W))
{
    Spritestate RealTime_Player = Spritestate.Player_Up;

if (keyboard.IsKeyDown(Keys.W))
{
    RealTime_Player = Spritestate.Player_Up;