Accord.Math.FourierTransform.DFT C# (CSharp) Method

        public static void DFT(Complex[] data, Direction direction)
        {
            int n = data.Length;
            double arg, cos, sin;
            var dst = new Complex[n];

            // for each destination element
            for (int i = 0; i < dst.Length; i++)
            {
                dst[i] = Complex.Zero;

                arg = -(int)direction * 2.0 * System.Math.PI * (double)i / (double)n;

                // sum source elements
                for (int j = 0; j < data.Length; j++)
                {
                    cos = System.Math.Cos(j * arg);
                    sin = System.Math.Sin(j * arg);

                    double re = data[j].Real * cos - data[j].Imaginary * sin;
                    double im = data[j].Real * sin + data[j].Imaginary * cos;

                    dst[i] += new Complex(re, im);
                }
            }

            // copy elements
            if (direction == Direction.Forward)
            {
                // devide also for forward transform
                for (int i = 0; i < data.Length; i++)
                    data[i] /= n;
            }
            else
            {
                for (int i = 0; i < data.Length; i++)
                    data[i] = dst[i];
            }
        }