In order to write a handler for the challenge-response event, we need to extend the WebViewClient class. We start by implementing a constructor that can take the credential information. This enables the activity that instantiates our class to manage the credential information and just pass it to our class during the class instantiation.

AuthWebViewClient

internal class AuthWebViewClient : WebViewClient
{
    public string Username { get; }
    public string Password { get; }
    private int LoginCount = 0;
    
    /// <summary>
    /// gets the user credentials for the impersonation process
    /// </summary>
    /// <param name="username"></param>
    /// <param name="password"></param>
    public AuthWebViewClient(string username, string password)
    {
        Username = username;
        Password = password;          
    }
    
    /// <summary>
    /// handles the authentication with the website.
    /// </summary>
    /// <param name="view"></param>
    /// <param name="handler"></param>
    /// <param name="host"></param>
    /// <param name="realm"></param>
    /// <remarks>
    /// </remarks>
    public override void OnReceivedHttpAuthRequest(WebView view, HttpAuthHandler handler, string host, string realm)
    {
        try
        {
            if (LoginCount < 3)
            {
                LoginCount++;
                handler.Proceed(Username, Password);
            }
            else
            {
                LoginCount = 0;
                handler.Cancel();
            }
        }
        catch (Exception ex)
        {
            Toast.MakeText(Application.Context, ex.Message, ToastLength.Long).Show();
        }
    }      
}