Xamarin Log User Out When 401 Unauthorized Response - api

Question

I have a Xamarin app that talks to an API. There is a certain scenario that happens when talking to the API in that a 401 (Unauthorized) exception is returned. This 401 (Unauthorized) is returned on purpose when the user account is made inactive so that even though the users token is still valid on the app they wouldn't be able to get any data back from the API.
I want to be able log the user out of the app, only when a 401 (Unauthorized) exception is thrown.
My API call looks like this:
public async Task<T> GetAsync<T>(string url)
{
_client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", _authToken?.AccessToken ?? this.GetToken().AccessToken);
var json = await _client.GetStringAsync(url);
return json.Deserialize<T>();
}
When the debugger reaches the var json = await _client.GetStringAsync(url); line a 401 (Unauthorized) exception is correctly thrown.
I want to be able to handle this 401 (Unauthorized) exception and log the user out of the app (preferably with an alert informing them of this).
I'm currently debugging on an Android device so I tried adding the following code to the MainActivity class.
protected override async void OnCreate(Bundle bundle)
{
AndroidEnvironment.UnhandledExceptionRaiser += AndroidEnvironmentOnUnhandledException;
}
private void AndroidEnvironmentOnUnhandledException(object sender, RaiseThrowableEventArgs e)
{
if(e.Exception.InnerException.GetBaseException().Message == "401 (Unauthorized)")
{
}
}
When the error is thrown I check if its a 401 (Unauthorized). It was here that I thought I would then log the user out of the app but I don't think this is the right direction.
Is there a best practice for handing this type of scenario that I am not aware of yet?

Answer 1

You could try to use try catch to warp var json = await _client.GetStringAsync(url) like the following code.
try
{
var json = await _client.GetStringAsync(url)
}
catch (WebException e)
{
using (WebResponse response = e.Response)
{
HttpWebResponse httpResponse = (HttpWebResponse)response;
Console.WriteLine("Error code: {0}", httpResponse.StatusCode);
using (Stream data = response.GetResponseStream())
using (var reader = new StreamReader(data))
{
// text is the response body
string text = reader.ReadToEnd();
if (text == "401 (Unauthorized)")
{
}
}
}
}