Cross Correlation in .NET - vb.net

Question

I am working on an app that takes two audio channels and compares them to find the phase difference (delay). I came across this post;
Calculating FFT Correlation Coefficient
which refers to this sample code;
https://dotnetfiddle.net/1nWIgQ
I got the code working with correct results after translating it to VB.NET (its the language I started with years ago in this app).
The problem I see is that when I change the signal generated from random noise to a sine wave, then the code gives crazy unrelated results. Any suggestions would be appreciated.
Code below;
Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports AForge.Math 'NuGet Package Aforge.Math module
Imports System.Runtime.InteropServices
Imports System.IO
Public Class Form2
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim c = New Xcorr4_2()
Dim size As Integer = 2048
Dim delay As Double
delay = 2
Dim signal1 = c.GenerateSignal(size)
Dim signal2 = c.GenerateSignal(size, delay)
Dim signal1Complex = c.ToComplexWithPadding(signal1, 2)
Dim fftSignal1 = c.FFT(signal1Complex)
Dim signal2Complex = c.ToComplexWithPadding(signal2, 2)
Dim fftSignal2 = c.FFT(signal2Complex)
Dim cc = c.CorrelationCoefficient(fftSignal1.ToArray(), fftSignal2.ToArray())
MsgBox(cc.Item1) 'correlation coeff
MsgBox(cc.Item2) 'recovered delay
End Sub
End Class
Class Xcorr4_2
Public Function CrossCorrelation(ByVal ffta As Complex(), ByVal fftb As Complex()) As Complex()
Dim conj = ffta.[Select](Function(i) New Complex(i.Re, -i.Im)).ToArray()
conj = conj.Zip(fftb, Function(v1, v2) Complex.Multiply(v1, v2)).ToArray()
FourierTransform.FFT(conj, FourierTransform.Direction.Backward)
Dim rr As Double() = New Double(conj.Length - 1) {}
rr = conj.[Select](Function(i) i.Magnitude).ToArray()
Return conj
End Function
Public Function CorrelationCoefficient(ByVal ffta As Complex(), ByVal fftb As Complex()) As Tuple(Of Double, Integer)
Dim tuble As Tuple(Of Double, Integer)
Dim correlation = CrossCorrelation(ffta, fftb)
Dim seq = correlation.[Select](Function(i) i.Magnitude)
Dim maxCoeff = seq.Max()
Dim maxIndex As Integer = seq.ToList().IndexOf(maxCoeff)
tuble = New Tuple(Of Double, Integer)(maxCoeff, maxIndex)
Return tuble
End Function
Public Function FFT(ByVal signal As Complex()) As Complex()
FourierTransform.FFT(signal, FourierTransform.Direction.Forward)
Return signal
End Function
Public Function IFFT(ByVal signal As Complex()) As Complex()
FourierTransform.FFT(signal, FourierTransform.Direction.Backward)
Return signal
End Function
Public Function ToComplexWithPadding(ByVal sample As Double(), ByVal Optional padding As Integer = 1) As Complex()
Dim logLength As Double = Math.Ceiling(Math.Log(sample.Length * padding, 2.0))
Dim paddedLength As Integer = CInt(Math.Pow(2.0, Math.Min(Math.Max(1.0, logLength), 14.0)))
Dim complex As Complex() = New Complex(paddedLength - 1) {}
Dim samples = sample.ToArray()
Dim i As Integer = 0
While i < sample.Length
complex(i) = New Complex(samples(i), 0)
i += 1
End While
While i < paddedLength
complex(i) = New Complex(0, 0)
i += 1
End While
Return complex
End Function
Public Function GenerateSignal(ByVal size As Integer, ByVal Optional shift As Integer = 0) As Double()
Dim list As List(Of Double) = New List(Of Double)()
Dim generator = New AForge.Math.Random.StandardGenerator()
' Changed original random signal to Sine wave below
For i As Integer = 0 To size - 1
'Dim randomNumber As Double = generator.[Next]()
'list.Add(randomNumber)
list.Add(Math.Sin(2 * Math.PI / 200 * i + shift))
Next
Dim list2 As List(Of Double) = New List(Of Double)()
For i As Integer = 0 To shift - 1
list2.Add(0)
Next
Dim ar = list.ToArray()
For i As Integer = 0 To size - shift - 1
list2.Add(ar(i))
Next
Return list2.ToArray()
End Function
End Class
Below is the output for original code vs the modified code with sine wave.
Original code random signal
Modified with sine wave inputs