Xamarin Forms Webview EvaluateJavaScriptAsync error on IOS - xamarin

Question

I work with an application made in Xamarin Forms that works on Android and IOS. I use a webview with a html and inside this html I call a javascript function when I login.
On Android it works fine but on IOS it doesn't work.
I read and apparently the error is due to the change from UIWebview to WKWebview, but so far I don't know how to fix this error.
I made my application on Windows in Visual Studio 2019, on the simulator device it works but on a physical device it doesn't work. In this case on Iphone not works.
This is my code:
LoginPage.xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MyLogin.Views.LoginPage">
<ContentPage.Content>
<StackLayout VerticalOptions="Center" HorizontalOptions="Center">
<Label Text="Sign In" FontAttributes="Bold" FontSize="Title" HorizontalOptions="Center" VerticalOptions="Center" HeightRequest="50" />
<Entry x:Name="emailEntry"
Grid.Row="2"
BackgroundColor="#31FFFFFF"
Placeholder="Email"
PlaceholderColor="#3AAAF4" />
<Entry x:Name="passwordEntry"
Grid.Row="3"
Margin="0,0,0,0"
BackgroundColor="#31FFFFFF"
IsPassword="True"
Placeholder="Password"
PlaceholderColor="#3AAAF4" />
<Button Text="Login" Clicked="OnLoginButtonClicked" BackgroundColor="#3AAAF4" TextColor="White" CornerRadius="8" />
<Label></Label>
<Label x:Name="messageLabel" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" WidthRequest="50" TextColor="Black" FontAttributes="Bold" />
<WebView x:Name="webView" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" IsVisible="false" />
</StackLayout>
</ContentPage.Content>
</ContentPage>
LoginPage.cs
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using Plugin.DeviceInfo;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
using Microsoft.CSharp;
using System.Net;
using System.IO;
using System.Reflection;
using Xamarin.Essentials;
using System.Web;
namespace MyLogin.Views
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class LoginPage : ContentPage
{
public string BlackboxString = "";
public LoginPage()
{
InitializeComponent();
webView.Source = LoadHTMLFileFromResource();
}
async void OnLoginButtonClicked(object sender, EventArgs e)
{
var blackbox = "";
blackbox = await webView.EvaluateJavaScriptAsync($"getBlackbox()");
//Code to login
}
private string GetLocalAddress()
{
var IpAddress = Dns.GetHostAddresses(Dns.GetHostName()).FirstOrDefault();
if (IpAddress != null)
return IpAddress.ToString();
return "Could not locate IP Address";
}
HtmlWebViewSource LoadHTMLFileFromResource()
{
var source = new HtmlWebViewSource();
// load HTML embed in PCL
var assembly = typeof(MainPage).GetTypeInfo().Assembly;
var stream = assembly.GetManifestResourceStream("mypage.mypagename.html");
using (var reader = new StreamReader(stream))
{
source.Html = reader.ReadToEnd();
}
return source;
}
}
}
Please help me,
Thanks