How to return multiple values from api to HttpClient Post

Question

I need help with returning multiple values from my api to the httpclient post request but its returning null

api

[HttpPost("ShowUser")]
    public (IEnumerable<UserInformation>, int) ShowUser([FromBody] Pagination pagination)
    { // retrieving data from database 
        var result = _showUsers.ShowManagerUsers(pagination.PageSize, pagination.skip, pagination.searchValue); // the output here is({System.Collections.Generic.List<Entities.UserInformation>}, 37) (note: 37 is the rows total)
        Entities.PaginationResponse<IEnumerable<UserInformation>> paginationResponse = new Entities.PaginationResponse<IEnumerable<UserInformation>>
        {
            Data = result.Item1,
            RowsCount = result.Item2
        };
        return (paginationResponse.Data, paginationResponse.RowsCount);
    }

HttpClient Post Request

public async Task<(List<TOut>, TOut)> PostGetListRequest<TIn, TOut>(TIn content, string uri, string token)
    {
            ...

            using (response = await client.PostAsync(uri, serialized))
            {
                if (response.StatusCode.ToString() == "OK")
                {
                    responseBody =  response.Content.ReadAsStringAsync().Result;
                    var result = JsonConvert.DeserializeObject<(List<TOut>, TOut)>(responseBody);
                    return (result.Item1, result.Item2);
                }
                  ...
            }
    }

Output

Any idea what's wrong with my code?

Answer 1

1. For the empty response body, if your project version is beyond ASP.NET Core 3.x, be sure add NewtonSoft support, check detailed steps in this answer

   services.AddControllers()
       .AddNewtonsoftJson();
   

2. Assume that the PostGetListRequest<TIn, TOut> method is invoked by using the following code, TOut is type of UserInformation class:

   await GetListRequest<string, UserInformation>("xxx", "https://localhost:portNumber/xxx", "xxx");
   

   So the deserialize type should be (List<UserInformation>, UserInformation).

   var result = JsonConvert.DeserializeObject<(List<TOut>, TOut)>(responseBody);
   

   But your API's return type is (IEnumerable<UserInformation>, int).

   public (IEnumerable<UserInformation>, int) ShowUser([FromBody] Pagination pagination)
   

   API's return type does not match the deserialize type. So you cannot deserialize successfully.

A working demo:

public async Task<(List<TOut>, int)> GetListRequest<TIn, TOut>(TIn content, string uri, string token)
{
    HttpClient client = new HttpClient();
    var response = await client.PostAsync(uri,serialized);
            
    var responseBody = response.Content.ReadAsStringAsync().Result;
    var result = JsonConvert.DeserializeObject<(List<TOut>, int)>(responseBody);
    return (result.Item1, result.Item2);
}

Api:

[HttpPost("ShowUser")]
public (IEnumerable<UserInformation>, int) ShowUser([FromBody] Pagination pagination)
{ // retrieving data from database 
    var result = _showUsers.ShowManagerUsers(pagination.PageSize, pagination.skip, pagination.searchValue); // the output here is({System.Collections.Generic.List<Entities.UserInformation>}, 37) (note: 37 is the rows total)
    Entities.PaginationResponse<IEnumerable<UserInformation>> paginationResponse = new Entities.PaginationResponse<IEnumerable<UserInformation>>
    {
        Data = result.Item1,
        RowsCount = result.Item2
    };
    return (paginationResponse.Data, paginationResponse.RowsCount);
}

Result:

Answer 2

Try changing your API code to this.

    [HttpPost("ShowUser")]
    public ActionResult ShowUser([FromBody] Pagination pagination)
    { // retrieving data from database 
        var result = _showUsers.ShowManagerUsers(pagination.PageSize, pagination.skip, pagination.searchValue); // the output here is({System.Collections.Generic.List<Entities.UserInformation>}, 37) (note: 37 is the rows total)
        Entities.PaginationResponse<IEnumerable<UserInformation>> paginationResponse = new Entities.PaginationResponse<IEnumerable<UserInformation>>
        {
            Data = result.Item1,
            RowsCount = result.Item2
        };
        return Ok((paginationResponse.Data, paginationResponse.RowsCount));
    }

If this is is designed to be an API that others will consume, you really shouldn't be returning anonymous objects. I think it would be a better idea to either return a wrapper model, or simply return the pagingResponse model you already have.

    [HttpPost("ShowUser")]
    [ProducesResponseType(typeof(Entities.PaginationResponse<IEnumerable<UserInformation>>), StatusCodes.Status200OK)]
    public ActionResult ShowUser([FromBody] Pagination pagination)
    { // retrieving data from database 
        var result = _showUsers.ShowManagerUsers(pagination.PageSize, pagination.skip, pagination.searchValue); // the output here is({System.Collections.Generic.List<Entities.UserInformation>}, 37) (note: 37 is the rows total)
        Entities.PaginationResponse<IEnumerable<UserInformation>> paginationResponse = new Entities.PaginationResponse<IEnumerable<UserInformation>>
        {
            Data = result.Item1,
            RowsCount = result.Item2
        };
        return Ok(paginationResponse);
    }

Let me know if this doesn't work or if you need anything else.

Happy coding!

Answer 3

1-you should await for reading response content

                    responseBody =  await response.Content.ReadAsStringAsync();

2-Make Sure the response in not empty.

3- i discourage using tuples as it violates the Object orinted and clean code practices