Proper Example

using System;
using System.Collections.Generic;
using System.Linq;
using SFML.System;
using SFML.Graphics;
using SFML.Window;
namespace Example
{
    class MainClass
    {
        private static RenderWindow _window;

        public static void Main(string[] args)
        {
            Random R = new Random();
            _window = new RenderWindow(new VideoMode(800, 600), "SFML window");
            ParticleSystem particles = new ParticleSystem(1000);
            Clock clock = new Clock();
            _window.SetVisible(true);
            _window.SetFramerateLimit(60);
            _window.Closed += new EventHandler(OnClosed);
            while (_window.IsOpen)
            {
                Vector2i mouse = Mouse.GetPosition(_window);
                particles.SetEmitter(new Vector2f(mouse.X, mouse.Y));
                particles.Update(Time.FromMilliseconds(50), R);
                _window.DispatchEvents();
                _window.Clear(Color.Black);
                _window.Draw(particles);
                _window.Display();
            }
        }
        private static void OnClosed(object sender, EventArgs e)
        {
            _window.Close();
        }
    }
    class ParticleSystem : Transformable, Drawable
    {
        public VertexArray m_vertices;
        public Time m_lifetime;
        public List<Particle> m_particles;
        public Vector2f m_emitter;

        public ParticleSystem(uint count)
        {
            m_particles = new List<Particle>((int)count);
            m_emitter = new Vector2f(0, 0);
            m_vertices = new VertexArray(PrimitiveType.Points);
            for (int i = 0; i != count; i++)
            {
                m_vertices.Append(new Vertex(m_emitter, Color.White));
            }
            m_lifetime = Time.FromSeconds(3);
            for (int i = 0; i < count; i++)
            {
                m_particles.Add(new Particle());
            }
        }
        public void Draw(RenderTarget target, RenderStates states)
        {
            states.Texture = null;
            states.Transform *= Transform;
            target.Draw(m_vertices, states);
        }

        public void Update(Time Elapsed, Random R)
        {
            for(int i = 0; i != m_particles.Count(); i++)
            {
                var temp = m_vertices[(uint)i];
                m_particles[i].lifetime -= Elapsed / 2;
                if (m_particles[i].lifetime <= Time.Zero)
                {
                    float Angle = ((R.Next() % 360) * 3.14f) / 180;
                    float Speed = ((R.Next() % 50) + 50) / 3f;

                    m_particles[i].velocity = new Vector2f(
                        (float)Math.Cos(Angle) * Speed,
                        (float)Math.Sin(Angle) * Speed);
                    m_particles[i].lifetime = Time.FromMilliseconds((R.Next()%2000)+1000);
                    temp.Color = Color.White;
                    temp.Position = m_emitter;
                }
                temp.Position += m_particles[i].velocity * .125f;
                float ratio =
                    m_particles[i].lifetime.AsSeconds() / m_lifetime.AsSeconds();
                temp.Color.A = (byte)(ratio * 255);
                m_vertices[(uint)i] = temp;
            }
        }
        public void SetEmitter(Vector2f newEmitter)
        {
            m_emitter = newEmitter;
        }
        public class Particle
        {
            public Vector2f velocity;
            public Time lifetime;
        }
    }
}