Debugger Stops while Parsing Rest API response HttpClient, Xamarin Forms

Question

I am trying to parse response from ASP.NET Core Web API. I am able to parse the response JSON into C# object successfully but app crashes without throwing any error when the parsed C# object is returned to the ViewModel.

in ViewModel

ApiResponse response = await _apiManager.GetAsync<ApiResponse>("authentication/GetUserById/1");

Response JSON:

{
"result": {
    "id": 1,
    "userType": 1,
    "firstName": “FirstName”,
    "middleName": null,
    "lastName": “LastName”,        
},
"httpStatusCode": 200,
"httpStatusDescription": "200OkResponse",
"success": true,
"message": "hello"

}

HttpClient GetAsync() method:

 public async Task<TResult> GetAsync<TResult>(string endpoint)
    {
        HttpResponseMessage httpResponse = _httpClient.GetAsync(endpoint).GetAwaiter().GetResult();
        httpResponse.EnsureSuccessStatusCode();
        TResult t = default(TResult);
        if (httpResponse.IsSuccessStatusCode)
        {
            string serialized = await httpResponse.Content.ReadAsStringAsync();

            t =  JsonConvert.DeserializeObject<TResult>(serialized);
        }
        return t;
    }

App crashes (debugger stops without any error) at "return t" statement. Here, _httpClient is a singleton object of HttpClient using DI.

TResult model is ApiResponse object

public class User
{
    [JsonProperty("id")]
    public int UserId { get; set; }
    [JsonProperty("userType")]
    public int UserType { get; set; }
    [JsonProperty("firstName")]
    public string FirstName { get; set; }
    [JsonProperty("middleName")]
    public string MiddleName { get; set; }
    [JsonProperty("lastName")]
    public string LastName { get; set; }        
}

public abstract class ResponseBase
{
    [JsonProperty("httpStatusCode")]
    public int HttpStatusCode { get; protected set; }
    [JsonProperty("httpStatusDescription")]
    public string HttpStatusDescription { get; protected set; }
    [JsonProperty("success")]
    public bool Success { get; protected set; }
    [JsonProperty("message")]
    public string Message { get; protected set; }
}

public class ApiResponse : ResponseBase
{
    [JsonProperty("result")]
    public User Result { get; set; } = new User();
}

There are two issues: 1. when the following statement executes, app crashes and debugger stops without throwing any error.

HttpResponseMessage httpResponse = await _httpClient.GetAsync(endpoint).ConfigureAwait(false);

But when GetAsync() is called with .GetAwaiter().GetResult(), network call is placed successfully. I do not understand why ConfigureAwait(false) fails.

HttpResponseMessage httpResponse = _httpClient.GetAsync(endpoint).GetAwaiter().GetResult();

why the following call fails and app crashes? How can I return parsed C# object to the calling code?

return JsonConvert.DeserializeObject(serialized);

Please advise.

When I try to run the same code in ASP.NET Core MVC, it works. It does not stop the debugger. The method GetAsync() returns the response to the calling code without any error. Code breaks only when I run the same on iOS simulator using Xamarin Forms — Tisha Anand, Jun 22 '19 at 08:14
If you change `return t;` to `return new ApiResponse{....}`, will it stop again? — Edward, Jun 24 '19 at 03:14
sorry for delayed response as I was busy with some other projects. I found an interesting thing when I put the breakpoint on the statement below the ConfigureAwait(false) statement, everything works fine. But the app crashes when the breakpoint is put on the statement which includes ConfigureAwait(false) method. — Tisha Anand, Jun 28 '19 at 18:04

score 0 · Answer 1 · answered Jun 22 '19 at 07:49

0

Try this

try
{
    var result = await httpClient.GetAsync(endpoint);
    var response = await result.Content.ReadAsStringAsync();
    data = JsonConvert.DeserializeObject<TResult>(response);
} 
catch (Exception exp)
{
   Console.Write(exp.InnerMessage);
}

Make sure that you have installed Newtonsoft.Json

answered Jun 22 '19 at 07:49

Argon

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1
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There is no problem in parsing the code. Code breaks only when return t executes. – Tisha Anand Jun 22 '19 at 08:15
Then try using ApiResponse model to parse – Argon Jun 22 '19 at 08:17
You mean to say in place of TResult, I should use ApiResponse class. The code that invokes GetAsync() method of HttpClient is ApiResponse response = await _apiManager.GetAsync("authentication/GetUserById/1"); – Tisha Anand Jun 22 '19 at 08:30

Debugger Stops while Parsing Rest API response HttpClient, Xamarin Forms

1 Answers1