Object is null after JsonConvert.DeserializeObject - asp.net

Question

I have looked at some forum posts and found no solution to my problem, so now I ask you for help. First i show you what the result of my HttpGet is and then i show you the not working deserialization.
Working example: I use the same code for an HttpGet to get a json result.
[HttpGet]
[Route("~/get_new_authtoken")]
public async Task<IActionResult> GetNewAuthTokenAsync()
{
try
{
HttpClient client = new HttpClient();
client.BaseAddress = new Uri("https://testApi/WebService/");
string APIConnection = _configuration.GetValue<string>("APIConnection");
HttpResponseMessage response = client.PostAsync("authtoken", new StringContent(string.Format(APIConnection))).Result;
if (response.IsSuccessStatusCode)
{
var token = JsonConvert.DeserializeObject<AuthToken>(await response.Content.ReadAsStringAsync());
return Ok(response.Content.ReadAsStringAsync().Result);
}
else
{
return BadRequest(response.Content.ReadAsStringAsync().Result);
}
}
catch (Exception ex)
{
SentrySdk.CaptureException(ex);
return Ok(ex.Message);
}
}
with following result when i call it via Postman
Not working deserialization: I store the token in a database and want to update it when it expires.
Object i want to desiralize in:
public class AuthToken
{
[JsonPropertyName("access_token")] public string AccessToken { get; set; }
[JsonPropertyName("refresh_token")] public string RefreshToken { get; set; }
[JsonPropertyName("token_type")] public string TokenType { get; set; }
[JsonPropertyName("expires_in")] public int ExpiresIn { get; set; }
}
when i add the following code to the httpget above to test the deserializationthe object Authtoken is always null.
AuthToken newAccessToken = new AuthToken();
newAccessToken = JsonConvert.DeserializeObject<AuthToken>(await response.Content.ReadAsStringAsync());
Like this->
if (response.IsSuccessStatusCode)
{
//To test
AuthToken newAccessToken = new AuthToken();
newAccessToken = JsonConvert.DeserializeObject<AuthToken>(await response.Content.ReadAsStringAsync());
//To test
var token = JsonConvert.DeserializeObject<AuthToken>(await response.Content.ReadAsStringAsync());
return Ok(response.Content.ReadAsStringAsync().Result);
}
else
{
return BadRequest(response.Content.ReadAsStringAsync().Result);
}
Updated the testint to following code:
AuthToken newAccessToken = new AuthToken();
var responseString = await response.Content.ReadAsStringAsync();
newAccessToken = JsonConvert.DeserializeObject<AuthToken>(responseString);
result of the responseString:

Answer 1

JsonPropertyNameAttribute is from System.Text.Json while JsonConvert.DeserializeObject is part of Newtonsoft.Json either switch to former completely by using System.Text.Json.JsonSerializer.Deserialize:
AuthToken newAccessToken = JsonSerializer.Deserialize<AuthToken>(...);
// or just use ReadFromJsonAsync instead of ReadAsStringAsync
Or use attributes for latter:
public class AuthToken
{
[JsonProperty("access_token")]
public string AccessToken { get; set; }
// ...
}