create a pitch tracker in csharp

main.cs
using System;
using System.Numerics; // required for complex numbers

public class PitchTracker {
   private const int SampleRate = 44100; // CD-quality audio
   
   public double GetPitch(double[] audioSamples) {
      // create a Hamming window with the same length as the audio sample
      double[] window = CreateHammingWindow(audioSamples.Length);
      // apply the window to the audio samples
      double[] windowedSamples = ApplyWindow(audioSamples, window);
      // apply the FFT algorithm to the windowed samples
      Complex[] spectrum = FFT(windowedSamples);
      // get the magnitude of the spectrum (to ignore phase)
      double[] magnitudes = GetMagnitude(spectrum);
      // find the index of the peak magnitude (ignore DC and Nyquist frequencies)
      int peakIndex = FindPeakIndex(magnitudes, SampleRate / 2);
      // convert the index to a frequency value (in Hz)
      double pitch = (double)peakIndex * SampleRate / audioSamples.Length;
      return pitch;
   }
   
   private double[] CreateHammingWindow(int length) {
      double[] window = new double[length];
      for (int i = 0; i < length; i++) {
         window[i] = 0.54 - 0.46 * Math.Cos(2 * Math.PI * i / (length - 1));
      }
      return window;
   }
   
   private double[] ApplyWindow(double[] samples, double[] window) {
      double[] windowedSamples = new double[samples.Length];
      for (int i = 0; i < samples.Length; i++) {
         windowedSamples[i] = samples[i] * window[i];
      }
      return windowedSamples;
   }
   
   private Complex[] FFT(double[] samples) {
      Complex[] spectrum = new Complex[samples.Length];
      for (int k = 0; k < samples.Length; k++) {
         Complex sum = 0;
         for (int n = 0; n < samples.Length; n++) {
            sum += samples[n] * Complex.Exp(-2 * Math.PI * k * n / samples.Length * Complex.ImaginaryOne);
         }
         spectrum[k] = sum;
      }
      return spectrum;
   }
   
   private double[] GetMagnitude(Complex[] spectrum) {
      double[] magnitudes = new double[spectrum.Length];
      for (int i = 0; i < spectrum.Length; i++) {
         magnitudes[i] = spectrum[i].Magnitude;
      }
      return magnitudes;
   }
   
   private int FindPeakIndex(double[] values, int maxIndex) {
      int peakIndex = 0;
      double peakValue = 0;
      for (int i = 1; i < maxIndex; i++) {
         if (values[i] > peakValue) {
            peakValue = values[i];
            peakIndex = i;
         }
      }
      return peakIndex;
   }
}
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