using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WindowsFormsApplication1
{
    using System;
    using System.Security.Cryptography;

    /// <summary>
    /// Represents a random number generator, a device that produces a sequence of numbers that meet cryptographic requirements for randomness.
    /// </summary>
    /// <remarks>
    /// Seed values are meaningless because this class uses a cryptographic service provider internally rather than a pseudo-random sequence.
    /// </remarks>
    public class CryptoRandom : Random, IDisposable
    {
        /// <summary>
        /// The internal random number generator.
        /// </summary>
        private readonly RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();

        /// <summary>
        /// Returns a random number between 0.0 and 1.0.
        /// </summary>
        /// <returns>
        /// A double-precision floating point number greater than or equal to 0.0, and less than 1.0.
        /// </returns>
        /// <remarks>
        /// Uses a cryptographic service provider internally rather than a pseudo-random sequence.
        /// </remarks>
        protected override double Sample()
        {
            var data = new byte[8];
            ulong number;

            do
            {
                // Get 8 random bytes.
                rng.GetBytes(data);

                // Convert the bytes to an unsigned 64-bit number.
                number = BitConverter.ToUInt64(data, 0);
            }
            while (number == ulong.MaxValue); // The result must be less than 1.0

            // Divide the number by the largest possible unsigned 64-bit number to get a value in the range 0.0 <= N < 1.0.
            return Convert.ToDouble(number) / Convert.ToDouble(ulong.MaxValue);
        }


        #region IDisposable Support

        private bool disposedValue; // To detect redundant calls

        // IDisposable
        protected virtual void Dispose(bool disposing)
        {
            if (!this.disposedValue)
            {
                if (disposing)
                {
                    // Dispose the underlying cryptographic random number generator.
                    rng.Dispose();
                }
            }

            this.disposedValue = true;
        }

        // This code added to correctly implement the disposable pattern.
        public void Dispose()
        {
            // Do not change this code.  Put cleanup code in Dispose(bool disposing) above.
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        #endregion
    }
}