Explosions

Code from internet

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using System;

namespace Explosion
{
    class Explosion
    {
        double drag = 0.8;
        Color particleColor = new Color(255, 230, 128, 255);
        double maxAge = 3;
        double age = 0;
        struct particle
        {
            public double x;
            public double y;
            public double vx;
            public double vy;
        }
        particle[] particles = new particle[100];
        Random rnd = new Random(127);
        Texture2D pixel;

        public Explosion (GraphicsDevice graph, int locx, int locy, float speed, Random rndm)
        {
            double angle;
            double radius;
            pixel = new Texture2D(graph, 1, 1);
            pixel.SetData<Color>(new Color[] { Color.White });
            if (speed == 0) speed = 2;
            rnd = rndm; // Remove this line to give each explosion the same animation
            for (int tel= 0; tel < 100; tel++)
            {
                particles[tel] = new particle();
                angle = rnd.NextDouble() * 2 * Math.PI;
                radius = Math.Pow(rnd.NextDouble(), 0.5);

                particles[tel].x = locx;
                particles[tel].y = locy;
                particles[tel].vx = speed * radius * Math.Sin(angle);
                particles[tel].vy = speed * radius * Math.Cos(angle);
            }
        }  

        public bool Update(GameTime gametime)
        {
            double timeChange = gametime.ElapsedGameTime.TotalSeconds;
            double localDrag = Math.Pow(drag, timeChange);
            age += gametime.ElapsedGameTime.TotalSeconds;
            if (age > maxAge) return false;

            for (int tel =0;tel < 100; tel++)
            { 
                particles[tel].vx *= localDrag;
                particles[tel].vy *= localDrag;
                particles[tel].x += particles[tel].vx * localDrag;
                particles[tel].y += particles[tel].vy * localDrag;
            }
            return true;
        }

        public void Draw (SpriteBatch spriteBatch)
        {
            Rectangle destination;
            for (int tel = 0; tel < 100; tel++)
            {
                destination = new Rectangle((int)particles[tel].x, (int)particles[tel].y, 5, 5);
                spriteBatch.Draw(pixel, destination, particleColor);
            }
        }
    }
}

Using

Declare variables

double timer;
List<Explosion> explosions = new List<Explosion>();
Random rnd = new Random(101);

Update additions

List<int> delList = new List<int>();

timer += gameTime.ElapsedGameTime.TotalSeconds;
if (timer > 0.6)
{
     timer = 0;
     Explosion newExplosion = new Explosion(GraphicsDevice, rnd.Next(GraphicsDevice.Viewport.Width), 
         rnd.Next(GraphicsDevice.Viewport.Height), rnd.Next(21)+1, rnd);
     explosions.Add(newExplosion);
}

foreach (Explosion expl in explosions)
{
     if (expl.Update(gameTime)) continue;
     delList.Add(explosions.IndexOf(expl));
}

for (int tel = explosions.Count; tel >= 0; tel--)
     if (delList.Exists(x => x == tel)) { explosions.RemoveAt(tel); }

Draw additions

spriteBatch.Begin();
foreach(Explosion expl in explosions)
{
     expl.Draw(spriteBatch);
}
spriteBatch.End();