Chain validation failed: .NET MAUI 9 Android App and Azure Web App

This is from long time ago. But I remember in Xamarin I used to have problems with HttpClient when trying to access HTTPS endpoint.

I solved those problems by using HttpClient with HttpMessageHandler on Android:

    public interface INativeHttpMessageHandlerProvider
    {
        HttpMessageHandler Get();
    }


    public static class HttpClientProvider
    {
        public static HttpClient Get()
        {
            if (Device.RuntimePlatform == Device.Android)
            {
                var nativeHttpMessageHandler = DependencyService.Get<INativeHttpMessageHandlerProvider>().Get();
                return new HttpClient(nativeHttpMessageHandler);    // nativeHttpMessageHander is injected from Android project
            }
            else
            {
                return new HttpClient();
            }
        }
    }

On your Android project

 public class AndroidHttpMessageHandlerProvider : INativeHttpMessageHandlerProvider
 {
     public HttpMessageHandler Get()
     {
         return new AndroidClientHandler();
     }
 }

Then I was just using HttpClient like this:

HttpClient client = HttpClientProvider.Get();

• Again, this is old Xamarin days, so I don't remember in which Android version this used to happen, nevertheless, I hope it helps. I don't remember finding this issue on Maui.

The problem is related to the default HttpClientHandler. Using SocketsHttpHandler I solved the problem.

Working HttClient instance:

_client = new HttpClient(new SocketsHttpHandler())