Where to store tokens in a xamarin.form application

Question

I have the class below that will be used in a xamarin.forms mobile application to retrieve the token generated by OAuth(webapi). Once this is generated I need to store in a place where I can access it again and not generating this all the time. Where is the best place to store this in the Pcl? I will also want to be able to remove this once the user logs off.

        class LoginService
        {
            public async Task Login(string username, string password)
            {
                HttpWebRequest request = new HttpWebRequest(new Uri(String.Format("{0}Token", Constants.BaseAddress)));
                request.Method = "POST";

                string postString = String.Format("username={0}&password={1}&grant_type=password", 
                HttpUtility.HtmlEncode(username), HttpUtility.HtmlEncode(password));
                byte[] bytes = Encoding.UTF8.GetBytes(postString);
                using (Stream requestStream = await request.GetRequestStreamAsync())
                {
                    requestStream.Write(bytes, 0, bytes.Length);
                }

                try
                {
                    HttpWebResponse httpResponse =  (HttpWebResponse)(await request.GetResponseAsync());
                    string json;
                    using (Stream responseStream = httpResponse.GetResponseStream())
                    {
                        json = new StreamReader(responseStream).ReadToEnd();
                    }
                    TokenResponseModel tokenResponse = JsonConvert.DeserializeObject(json);
                    return tokenResponse.AccessToken;
                }
                catch (Exception ex)
                {
                    throw new SecurityException("Bad credentials", ex);
                }
            }
        }

Answer 1

Just an update for anyone searching, as things have changed since this post was created. It is not advised to use the following any more:

Application.Current.Properties

To securely store things like access tokens etc you can use the Xamarin.Essentials SecureStorage static class.

Just add the Xamarin.Essentials nuget package if you don't already have it and use it like so:

using Xamarin.Essentials;
.
.
.

await SecureStorage.SetAsync("someKey", "someValue");

var myValue = await SecureStorage.GetAsync("someKey");

you also have the option to

SecureStorage.Remove("someKey");
//or 
SecureStorage.RemoveAll();

Refer this for more documentation