collision detection xna

Question

Hello to all,
I made a simple program, like described here:
https://jamessadlier.wordpress.com/tutorials/xna-4-0-collision-detection/
to detect a collision in XNA and to bounce the ball off the block and of the wall.
(I have a "pics" Folder where I have the both pictures: the ball and the block.) But nothing happens. The ball doesn't move at all. What am I doing wrong?

What I have tried:

I tried this code and read related literature

 

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 game19Addition
{
    // This is the main type for your game
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        //this class has a property: GraphicsDevice that represents  the actual graphics device on your PC.
        //everything you do on screen in your XNA games will run through this object
        GraphicsDeviceManager graphics;

        //this is the core object to to draw sprites(2d or 3d image inegrated into a large scene)
        SpriteBatch spriteBatch;

        Texture2D spriteTexture1;
        Rectangle ballBounds;
        Vector2 ballPosition;
        Vector2 ballVelocity;

        Texture2D spriteTexture2;
        Rectangle blockBounds;
        Vector2 blockPosition;

        public Game1()
        {
            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

            ballPosition = new Vector2(this.GraphicsDevice.Viewport.Width / 2,
                                            this.GraphicsDevice.Viewport.Height * 0.25f);
            ballVelocity = new Vector2(0, 1);
            spriteTexture1 = Content.Load<Texture2D>(@"pics/ball");
            ballBounds = new Rectangle((int)(ballPosition.X - spriteTexture1.Width / 2),
                                (int)(ballPosition.Y - spriteTexture1.Height / 2),
                                spriteTexture1.Width,
                                spriteTexture1.Height);

            blockPosition = new Vector2(this.GraphicsDevice.Viewport.Width / 2,
                                              this.GraphicsDevice.Viewport.Height * 0.75f);

            spriteTexture2 = Content.Load<Texture2D>(@"pics/block");
            //create rectangles based off the size of the textures
            blockBounds = new Rectangle((int)(blockPosition.X - spriteTexture2.Width / 2),
                                            (int)(blockPosition.Y - spriteTexture2.Height / 2),
                                            spriteTexture2.Width,
                                            spriteTexture2.Height);
        }
        /// <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 (Keyboard.GetState().IsKeyDown(Keys.F12))
                this.Exit();

            // TODO: Add your update logic here
            if (ballBounds.Intersects(blockBounds) || !GraphicsDevice.Viewport.Bounds.Contains(ballBounds))
            {
                ballVelocity = -ballVelocity;
                ballPosition += ballVelocity;
            }
            else
            {
                ballPosition += ballVelocity;
            }

            //update boundig boxes
            ballBounds.X = (int)ballPosition.X;
            blockBounds.Y = (int)ballPosition.Y;

            blockPosition.X = (int)blockPosition.X;
            blockPosition.Y = (int)blockPosition.Y;

            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);

            spriteBatch.Begin();
            spriteBatch.Draw(spriteTexture1, ballPosition, Color.White);
            spriteBatch.Draw(spriteTexture2, blockPosition, Color.White);
            spriteBatch.End();

            base.Draw(gameTime);
        }
    }
}