How to request Web API OAuth token using HttpClient in a C# WPF?

Question

I'm new in WPF and want to call oauth token api to get authenticated token through HttpClient. I have tried many solutions but still getting response Bad request(400).
I have checked with postman as well, api works fine.
postman response

Tried Solutions:
(1)

var request = new HttpRequestMessage(HttpMethod.Post, url);

request.Content = new FormUrlEncodedContent(param);
request.Content.Headers.ContentType = new MediaTypeHeaderValue("application/x-www-form-urlencoded");
request.Content.Headers.ContentType.CharSet = "UTF-8";

using (HttpResponseMessage response = await ApiHelper.apiClient.SendAsync(request))
{
    Console.WriteLine("postRequest -> StatusCode -> " + response.StatusCode);
    if (response.IsSuccessStatusCode)
    {
        //ComicModel comic = await response.Content.ReadAsAsync<ComicModel>();
        var responseString = await response.Content.ReadAsStringAsync();
        return response;
    }
    else
    {
        Console.WriteLine("postRequest -> exception -> " + response);
        throw new Exception(response.ReasonPhrase);
    }
}

(2)

using (var content = new FormUrlEncodedContent(param))
{
    content.Headers.Clear();
    content.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
    using (HttpResponseMessage response = await ApiHelper.apiClient.PostAsync(url, content))
    {
        Console.WriteLine("postRequest -> StatusCode -> " + response.StatusCode);
        if (response.IsSuccessStatusCode)
        {
            //ComicModel comic = await response.Content.ReadAsAsync<ComicModel>();
            var responseString = await response.Content.ReadAsStringAsync();
            return response;
        }
        else
        {
            Console.WriteLine("postRequest -> exception -> " + response);
            throw new Exception(response.ReasonPhrase);
        }
    }
}

(3)

using (HttpResponseMessage response = await ApiHelper.apiClient.PostAsync(url, new FormUrlEncodedContent(param)))
{
    Console.WriteLine("postRequest -> StatusCode -> " + response.StatusCode);
    if (response.IsSuccessStatusCode)
    {
        //ComicModel comic = await response.Content.ReadAsAsync<ComicModel>();
        var responseString = await response.Content.ReadAsStringAsync();
        return response;
    }
    else
    {
        Console.WriteLine("postRequest -> exception -> " + response);
        throw new Exception(response.ReasonPhrase);
    }
}

All solutions respond me 400 bad request.
My params are:

var params= new List<KeyValuePair<string, string>>();
            params.Add(new KeyValuePair<string, string>("grant_type", "password"));
            params.Add(new KeyValuePair<string, string>("username", HttpUtility.UrlEncode("myUsername")));
            params.Add(new KeyValuePair<string, string>("password", HttpUtility.UrlEncode("myPass")));

How can I fix it? Thank you in advance.

Answer 1

How do you authenticate with Postman? I do not see it in your code. It depends on how the api is configured. Be sure to use the appropriate auth method in your client call, for example Bearer token. Api should return 400 instead of 401.

httpClient.SetBearerToken(accessToken);

Answer 2

Oops. my base url starts with http. I forgot to replace it with https. Everything is fine with https: :)
Thanks