How to return a JSON result from inside using(){} block答案

【问题标题】：How to return a JSON result from inside using(){} blockHow to return a JSON result from inside using(){} block
【发布时间】：2022-12-02 00:59:04
【问题描述】：

My code looks like this:

using Newtonsoft.Json;
using System.Net.Http.Headers;
using TestApp.Model.StudentModel; 

namespace TestApp.Services
{

    public class TodoService
    {

        public string TodoURL { get; set; } = "https://******.***/api/student";
        StudentModel result; 

        public async Task<List<string>> GetTodoTypesAsync()
        {

            using (HttpClient client = new HttpClient())
            {
                // accept respose as json
                client.DefaultRequestHeaders.Accept.Add(
                    new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json")
                );

                // provide token with the request
                client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue(
                    "Basic", Convert.ToBase64String(
                        System.Text.ASCIIEncoding.ASCII.GetBytes(
                            string.Format("{0}:{1}", "", "*****"
                        )
                    )
                );

                HttpResponseMessage response = client.GetAsync(TodoURL).Result;
                response.EnsureSuccessStatusCode();
                string responseData = await response.Content.ReadAsStringAsync();
                result = JsonConvert.DeserializeObject<StudentModel>(responseData);
                return result; 

            }

        }

    }
    
}

But I get the following error when I run the app:

Severity Code Description Project File Line Suppression State Error CS0029 Cannot implicitly convert type 'TestApp.Model.StudentModel.StudentModel' to 'System.Collections.Generic.List' TestApp C:***\TestApp\Services\TodoService.cs 36 Active

It does not matter if I change
public async Task<List<string>> GetTodoTypesAsync()
to
public async Task<List<StudentModel>> GetTodoTypesAsync()
And this is a portion of the model StudentModel
namespace TestApp.Model.StudentModel
{
    public class Avatar
    {
        public string href { get; set; }
    }

    public class StudentModel
    {
        public string displayName { get; set; }
        public string id { get; set; }
    }
}

【问题讨论】：

Not related but please do not wrap the HttpClient into a using block rather reuse it multiple time against the same domain.
You really should inject that HttpClient.
client.GetAsync(TodoURL).Result oh god, you call that "code that worked"? You're begging for deadlocksandsocket starvation. This is incredibly poor code.
@Blindy He said he is a beginner. We all learn by failing, don't we? OP: I suggest you make yourself familiar with Stephen Cleary ;D <- That whole blog is liquid gold ...
@vaeon 1) change to Task<List<StudentModel>> GetTodoTypesAsync() 2) change to List<StudentModel> result; 3) change to result = JsonConvert.DeserializeObject<List<StudentModel>>(responseData); 4)missing a close parenthesis client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue . IMHO - make it work, then optimize later. Your code is def not production ready, so do heed the above cmets about HttpClient and def read Stephen Clearly blog

标签： c# .net generics blazor

【解决方案1】：

You should supply an example of the JSON but anyways...

You are deserializing your response to StudentModel, implying that your responsedata contains a single StudentModel.

If your responsedata is an Array you should Deserialize it as StudentModel[] or List.

If responsedata contains a single StudentModel then your method needs to return StudentModel not List

【讨论】：