如何在 C# 中使用 HttpClient 讀取 webapi 響應

Question

我對 webapi 相當陌生，並開發了一個小的 webapi，它有一些操作並返回我的自定義類，稱為Response 。

Response類

public class Response
{
    bool IsSuccess=false;
    string Message;
    object ResponseData;

    public Response(bool status, string message, object data)
    {
        IsSuccess = status;
        Message = message;
        ResponseData = data;
    }
}

我的 webapi 與操作

[RoutePrefix("api/customer")]
public class CustomerController : ApiController
{
    static readonly ICustomerRepository repository = new CustomerRepository();

    [HttpGet, Route("GetAll")]
    public Response GetAllCustomers()
    {
        return new Response(true, "SUCCESS", repository.GetAll());
    }

    [HttpGet, Route("GetByID/{customerID}")]
    public Response GetCustomer(string customerID)
    {
        Customer customer = repository.Get(customerID);
        if (customer == null)
        {
            throw new HttpResponseException(HttpStatusCode.NotFound);
        }
        return new Response(true, "SUCCESS", customer);
        //return Request.CreateResponse(HttpStatusCode.OK, response);
    }

    [HttpGet, Route("GetByCountryName/{country}")]
    public IEnumerable<Customer> GetCustomersByCountry(string country)
    {
        return repository.GetAll().Where(
            c => string.Equals(c.Country, country, StringComparison.OrdinalIgnoreCase));
    }
}

現在我遇到的問題是我不知道如何讀取從 webapi 操作返回的響應數據並從我的響應類中提取 json。 獲得 json 后，我如何將該 json deserialize客戶類。

這是我調用 webapi 函數的方式：

private void btnLoad_Click(object sender, EventArgs e)
{
    HttpClient client = new HttpClient();
    client.BaseAddress = new Uri("http://localhost:8010/");
    // Add an Accept header for JSON format.  
    //client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
    // List all Names.  
    HttpResponseMessage response = client.GetAsync("api/customer/GetAll").Result;  // Blocking call!  
    if (response.IsSuccessStatusCode)
    {
        Console.WriteLine("Request Message Information:- \n\n" + response.RequestMessage + "\n");
        Console.WriteLine("Response Message Header \n\n" + response.Content.Headers + "\n");
    }
    else
    {
        Console.WriteLine("{0} ({1})", (int)response.StatusCode, response.ReasonPhrase);
    }
    Console.ReadLine();   
}

請幫我整理我的代碼。

1. 如何獲取webapi在客戶端返回的響應類

2. 我如何從響應類中提取 json

3. 如何在客戶端將 json 反序列化為客戶類

謝謝

編輯：我使用此代碼但仍然出現錯誤。

    var baseAddress = "http://localhost:8010/api/customer/GetAll";
    using (var client = new HttpClient())
    {
        using (var response =  client.GetAsync(baseAddress).Result)
        {
            if (response.IsSuccessStatusCode)
            {
                var customerJsonString = await response.Content.ReadAsStringAsync();
                var cust = JsonConvert.DeserializeObject<Response>(customerJsonString);
            }
            else
            {
                Console.WriteLine("{0} ({1})", (int)response.StatusCode, response.ReasonPhrase);
            }
        }
    }

錯誤是：

Newtonsoft.Json.dll 中發生了“Newtonsoft.Json.JsonSerializationException”類型的異常，但未在用戶代碼中處理

附加信息：無法將當前 JSON 對象（例如 {"name":"value"}）反序列化為類型“WebAPIClient.Response[]”，因為該類型需要 JSON 數組（例如 [1,2,3]）才能正確反序列化.

為什么響應會導致此錯誤？

Answer 1

在客戶端，包括對內容的閱讀：

    HttpResponseMessage response = client.GetAsync("api/customer/GetAll").Result;  // Blocking call!  
    if (response.IsSuccessStatusCode)
    {
        Console.WriteLine("Request Message Information:- \n\n" + response.RequestMessage + "\n");
        Console.WriteLine("Response Message Header \n\n" + response.Content.Headers + "\n");
        // Get the response
        var customerJsonString = await response.Content.ReadAsStringAsync();
        Console.WriteLine("Your response data is: " + customerJsonString);

        // Deserialise the data (include the Newtonsoft JSON Nuget package if you don't already have it)
        var deserialized = JsonConvert.DeserializeObject<IEnumerable<Customer>>(custome‌​rJsonString);
        // Do something with it
    }

更改您的 WebApi 以不使用您的 Response 類，而是使用Customer的IEnumerable 。 使用HttpResponseMessage響應類。

您的 WebAPI 應該只需要：

[HttpGet, Route("GetAll")]
public IEnumerable<Customer> GetAllCustomers()
{
    var allCustomers = repository.GetAll();
    // Set a breakpoint on the line below to confirm
    // you are getting data back from your repository.
    return allCustomers;
}

根據評論中的討論添加了通用響應類的代碼，盡管我仍然建議您不要這樣做並避免調用您的類 Response。 您應該返回HTTP 狀態代碼而不是您自己的狀態代碼。 一個 200 Ok，一個 401 Unauthorised 等等。還有這篇關於如何返回 HTTP 狀態代碼的帖子。

    public class Response<T>
    {
        public bool IsSuccess { get; set; }
        public string Message { get; set; }
        public IEnumerable<T> ResponseData { get; set; }

        public Response(bool status, string message, IEnumerable<T> data)
        {
            IsSuccess = status;
            Message = message;
            ResponseData = data;
        }
    }

Answer 2

或者您可以在同一個電話中進行轉換

  TResponse responseobject = response.Content.ReadAsAsync<TResponse>().Result;
            responseJson += "hostResponse: " + JsonParser.ConvertToJson(responseobject);
            //_logger.Debug($"responseJson : {responseJson}", correlationId);