Upscaling with Point sampling in MonoGame

UpscalePoint.cs

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;

namespace WinDesktopPlatformer
{
    public class Game1 : Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;

        static int PPU = 1;
        static int TILE_SIZE = 16;
        static int ROOM_WIDTH = 32;
        static int ROOM_HEIGHT = 18;
        static Rectangle CANVAS = new Rectangle(0, 0, (TILE_SIZE * ROOM_WIDTH) / PPU, (TILE_SIZE * ROOM_HEIGHT) / PPU);

        Texture2D tileSet;

        Rectangle tile1;

        private const int ScreenWidth = 1920;
        private const int ScreenHeight = 1080;
        private RenderTarget2D _renderTarget;

        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            graphics.PreferMultiSampling = false;
            graphics.SynchronizeWithVerticalRetrace = true;
            graphics.PreferredBackBufferWidth = ScreenWidth;
            graphics.PreferredBackBufferHeight = ScreenHeight;

            graphics.IsFullScreen = true;

            Content.RootDirectory = "Content";
        }

        protected override void LoadContent()
        {
            spriteBatch = new SpriteBatch(GraphicsDevice);

            tileSet = Content.Load<Texture2D>(@"Images/Tiles2");
            tile1 = new Rectangle(0, 32, TILE_SIZE, TILE_SIZE);

            _renderTarget = new RenderTarget2D(GraphicsDevice, CANVAS.Width, CANVAS.Height);
        }

        protected override void Update(GameTime gameTime)
        {
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed || Keyboard.GetState().IsKeyDown(Keys.Escape))
                Exit();

            base.Update(gameTime);
        }

        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.SetRenderTarget(_renderTarget);
            GraphicsDevice.Clear(Color.CornflowerBlue);

            // render your complete game here at a low resolution to the render target
            // we use point sampling here because we enlarge the texture
            spriteBatch.Begin(samplerState: SamplerState.PointClamp);
            spriteBatch.Draw(tileSet, new Rectangle(16, 16, 64, 64), tile1, Color.White);
            spriteBatch.End();

            GraphicsDevice.SetRenderTarget(null);

            // here we upscale it to the full screen, again with point sampling enabled
            spriteBatch.Begin(samplerState: SamplerState.PointClamp);
            spriteBatch.Draw(_renderTarget, new Rectangle(0, 0, ScreenWidth, ScreenHeight), Color.White);
            spriteBatch.End();

            base.Draw(gameTime);
        }
    }
}