xamarin iOS webView post

I created a custom webViewRenderer in Xamarin in this way.

This is the class in Xamarin project

    public class PostWebView : WebView {

        public static readonly BindableProperty PostUrlProperty =
            BindableProperty.Create(nameof(PostUrl), typeof(string), typeof(PostWebView), string.Empty, BindingMode.OneWay);

        public string PostUrl {
            get { return (string)GetValue(PostUrlProperty); }
            set { SetValue(PostUrlProperty, value); }
        }

        public byte[] PostData { get; set; } = new byte[0];
    }

and this is the custom renderer in Android project

[assembly: ExportRenderer(typeof(PostWebView), typeof(PostWebViewRenderer))]
namespace AppWebView.Droid {

    //Custom renderer on the native project
    public class PostWebViewRenderer : WebViewRenderer {
        public PostWebViewRenderer(Context ctx) : base(ctx) { }

        protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e) {
            if (e.PropertyName == "PostUrl") {
                if (Control == null)
                    return;

                var ctlWebView = (Android.Webkit.WebView)Control;
                var view = Element as PostWebView;
                ctlWebView.PostUrl(view.PostUrl, view.PostData);
            }
        }
    }

}

So, now I'm trying to do the same in the iOS project

[assembly: ExportRenderer(typeof(WebView), typeof(AppWebView.iOS.PostWebViewRenderer))]
namespace AppWebView.iOS {
    // Xamarin.Forms.Platform.iOS.WebViewRenderer
    public class PostWebViewRenderer : ViewRenderer<PostWebView, WKWebView> {

        private WKWebView wkWebView;

        protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e) {
            base.OnElementPropertyChanged(sender, e);

            if (e.PropertyName == PostWebView.PostUrlProperty.PropertyName)
            {
                var aWebView = Element as PostWebView;

                if (aWebView.PostUrl != "")
                {
                    if (Control == null)
                    {
                        var config = new WKWebViewConfiguration();
                        wkWebView = new WKWebView(Frame, config);
                        SetNativeControl(wkWebView);
                    }

                    var request = new NSMutableUrlRequest(new NSUrl(new NSString(aWebView.PostUrl)));
                    //request.Body = NSData.FromData(NSData.FromArray(aWebView.PostData));
                    request.Body = NSData.FromString(aWebView.StringData);
                    request.HttpMethod = "POST";
                    // enable?...
                    //request["Content-Length"] = request.Body.Length.ToString();
                    //request["Content-Type"] = "application/x-www-form-urlencoded charset=utf-8";
                    Control.LoadRequest(request);
                }
                
            }
        }
    }

}

So, in XAML I put my own control

<local:PostWebView x:Name="postWebView1" Source="" HeightRequest="600" WidthRequest="100" /> 

in code-behind (it's only a test...) I create my request with parameters

            byte[] byteParams = await GetParamsAsync();

            postWebView1.PostData = byteParams;
            postWebView1.StringData = HttpUtility.UrlEncode(byteParams);
            postWebView1.PostUrl = "https://..../DispatcherServlet";

and this is GetParamsAsync

        public async Task<byte[]> GetParamsAsync() {

            var dataContent = new FormUrlEncodedContent(new[] {
                new KeyValuePair<string, string>("a", "avalue"),
                new KeyValuePair<string, string>("b", "bvalue",
                new KeyValuePair<string, string>("c", "cvalue"),
                new KeyValuePair<string, string>("d", "dvalue")
            });

            var s = await dataContent.ReadAsByteArrayAsync();

            return s;
        }

In Android emulator all works fine using PostData property.
In iOS emulator the webView is showing the page but the the way I "post" the parameters doesn't work... I tried in several different way (such as a new property StringData) with no luck.... I don't understand how can I do...

Finally I solved in this way

var request = new NSMutableUrlRequest(
    new NSUrl(new NSString(aWebView.PostUrl))
);                     
request.Body = NSData.FromArray(aWebView.PostBytesData);
request.HttpMethod = "POST";                     
request["Content-Length"] = request.Body.Length.ToString();   
request["Content-Type"] = "application/x-www-form-urlencoded charset=utf-8";