c# - 如何在 C# 中使用 HttpClient 读取 webapi 响应

Question

我开发了一个小型 webapi，它有一些操作并返回我的自定义类 Response。

Response 类

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

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

我的带有操作的 webapi

[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));
    }
}

现在我卡住了，我不知道如何读取从 webapi 操作返回的响应数据并从我的响应类中提取 json。获取 json 后，我如何反序列化那个 json 到客户类。

这是我调用 webapi 函数的方式:

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();   
}

问题

1. 如何在客户端获取webapi返回的响应类

2. 如何从响应类中提取 json

3. 如何在客户端反序列化json到客户类

---

我使用此代码但仍然出现错误。

    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);
            }
        }
    }

错误是:

An exception of type 'Newtonsoft.Json.JsonSerializationException' occurred in Newtonsoft.Json.dll but was not handled in user code

Additional information: Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'WebAPIClient.Response[]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.

为什么响应会导致此错误？

Answer 1

在客户端，包括阅读内容:

    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 类，而是使用 Customer 的 IEnumerable。使用 HttpResponseMessage 响应类。

您的 WebAPI 应该只需要:

[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;
}

根据评论中的讨论为通用响应类添加了代码，但我仍然建议您不要这样做并避免调用您的类 Response。你应该返回 HTTP status codes而不是你自己的。一个 200 Ok，一个 401 Unauthorised，等等。还有 this post关于如何返回 HTTP 状态代码。

    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;
        }
    }