OAuth 2.0 REST Web API 和 xamarin 表单

Question

I make webservice api based on this tutorial https://www.c-sharpcorner.com/article/asp-net-mvc-oauth-2-0-rest-web-api-authorization-using-database-first-approach/ and I need to consume the service form xamarin forms. But I don't know how to authorize client.

Answer 1

Before you try authorizing in code, you should try talking to your API via an api client such as Postman .

You can see in step 11 of the article you reference that the writer is infact doing this.

He is performing the following steps:

• Calling the token endpoint (no auth)
• Adding the token to his subsequent requests

In order to call an API with authorization, you must first know the auth method (basic, OAuth etc). In this case you're saying it's OAuth:

Take a look at the guide, it shares this picture:

To do this in code you will need to add the following header to your http client. Lets assume you're using vanilla System.Net.Http.HttpClient you would need to implement a class that looks something like this:

public class APIClient
{
    private HttpClient _client;

    public APIClient()
    {
        _client = SetupClient();
    }

    private HttpClient SetupClient()
    {
        //setup your client here
        var client = new HttpClient();

        //string oauthToken = TokenService.GetUserToken();
        string oauthToken = "eyJhbGciO......."; //Example token
        client.DefaultRequestHeaders.Add("Authorization", $"Bearer {oauthToken}");

        //more setup here

        return client;
    }

    public async Task<HttpResponseMessage> Get(string endpoint)
    {
        var request = new HttpRequestMessage(HttpMethod.Get, endpoint);

        return await CallAsync(request);
    }

    private async Task<HttpResponseMessage> CallAsync(HttpRequestMessage request)
    {
        //do things before?

        var result = await _client.SendAsync(request);

        //handle result? null? not success code?

        return result;
    }
}

When you initialise your HttpClient you should add the following header:

• Authorization : Bearer {yourtoken}

Now subsequent api requests will have authorization from your api client. How you set this bearer value is up to you. Some people store credentials in the xamarin main App class, and then retrieve the property. Other will persist the data into a plist and have the apiclient read this value (maybe credentials expire every 30 days).

Regardless there are a number of pitfalls that come with talking to api's from a xamarin app. You should always start by calling your api from outside of your app, from within an api client. This will teach you how to configure the requests correctly, without the overhead of worrying if your code/configuration is correct.

Answer 2

Please check my class if help you

   `public class ServicesClient
    {

        private HttpClient httpClient;
        private bool _IsConnection { get { return CheckInternet(); } }
        public bool IsConnection { get { return _IsConnection; } }


        public ServicesClient()
        {
            httpClient = new HttpClient(new HttpClientHandler());
            //You can change the key as you need and add value 
            httpClient.DefaultRequestHeaders.Add("key", "000000");
        }

        //Get Method
        public async Task<T> GetAsync<T>(string URL) where T : class
        {
            if (IsConnection)
            {
                    var result = await httpClient.GetStringAsync(URL);
                    if (!string.IsNullOrEmpty(result))
                        return JsonConvert.DeserializeObject<T>(result);
                    else
                        return null;
            }
            return null;
        }

        //Post Method
        public async Task<T> PostAsync<T>(string URL, object param) where T : class
        {
            if (IsConnection)
            {
                var json = JsonConvert.SerializeObject(param);
                var httpContent = new StringContent(json, Encoding.UTF8, "application/json");

                    var result = await httpClient.PostAsync(URL, httpContent);
                    if (result.IsSuccessStatusCode)

                            return JsonConvert.DeserializeObject<T>(result.Content.ReadAsStringAsync().Result);
            }
            return null;
        }

        bool CheckInternet()
        {
            return Connectivity.NetworkAccess == NetworkAccess.Internet;
        }
    }
}`