Question

我有一个调用web api的MVC应用程序来传递一些数据。

MVC编码

     [AcceptVerbs(HttpVerbs.Post)]
    public async System.Threading.Tasks.Task<ActionResult> StudentViewModels_Create([DataSourceRequest]DataSourceRequest request, [Bind(Prefix = "models")]IEnumerable<StudentViewModel> studentviewmodels)
    {
        using (System.Net.Http.HttpClient client = new System.Net.Http.HttpClient())
        {
            string  baseUrl = "http://localhost:51514/api/Students";
            client.BaseAddress = new Uri(baseUrl);
            client.DefaultRequestHeaders.Accept.Clear();
            client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));

            JArray postData = new JArray();
            //postData.Add(JsonConvert.SerializeObject(request));
            foreach(StudentViewModel student in studentviewmodels)
            {
                postData.Add(JsonConvert.SerializeObject(student));
            }
           // call the web-api and pass the data
           System.Net.Http.HttpResponseMessage response = await client.PostAsync(baseUrl, new StringContent(new JavaScriptSerializer().Serialize(postData), Encoding.UTF8, "application/json"));
            if (!response.IsSuccessStatusCode)
            {
                var data = response.Content.ReadAsStringAsync();
            }
        }

        // this will return new data
        //return Json("");
    }

这里是发送 postData 变量之前的数据的图片

但是，当调用到达Api时，Json数组为空。

网络-API

    public  IHttpActionResult Students_Create(JArray inputData)
    {

        var students = new List<Student>();

        for (int i = 1; i<inputData.Count; i++)
        {
            var tempStudent = new Student();
            tempStudent = (Student)JsonConvert.DeserializeObject(inputData[i].ToString());
            students.Add(tempStudent);
        }

        // Will keep the inserted entitites here. Used to return the result later.
        var entities = students;
        if (ModelState.IsValid)
        {
            using (var northwind = new StudentEntities())
            {
                foreach (var student in students)
                {
                    // Create a new Student entity and set its properties from the posted StudentViewModel.
                    var entity = new Student
                    {
                        Studentid = student.Studentid,
                        Firstname = student.Firstname,
                        Lastname = student.Lastname,
                        Age = student.Age
                    };
                    // Add the entity.
                    northwind.Students.Add(entity);
                    // Store the entity for later use.
                    entities.Add(entity);
                }
                // Insert the entities in the database.
                northwind.SaveChanges();
            }
        }

        return Json(db.Students);
    }

inputData 变量的图片

关于为什么会发生这种情况的任何想法？谢谢你的帮助。

Answer 1

不是答案，而是对您提供的代码的更多观察。您似乎无法在Students_Create中的任何位置调用StudentViewModels_Create方法。这导致我相信您将StudentViewModels_Create的返回结果传递给Students_Create，这将无效，因为StudentViewModels_Create返回一个空的Json对象（return Json("")）。

Answer 2

问题在于Json数组。 MVC代码部分

中的这段代码

        JArray postData = new JArray();
        //postData.Add(JsonConvert.SerializeObject(request));
        foreach(StudentViewModel student in studentviewmodels)
        {
            postData.Add(JsonConvert.SerializeObject(student));
        }

当我通过序列化器传递数组时

       var serializer = new JavaScriptSerializer();
       var json = new System.Web.Script.Serialization.JavaScriptSerializer().Serialize(postData);
       var stringContent = new StringContent(json, Encoding.UTF8, "application/json");

       // pass the data to the api
       System.Net.Http.HttpResponseMessage response = await client.PostAsync(baseUrl, stringContent);

json varaible只包含一个空数组，所以传递给api的是一个空数组。因此我为什么只得到一个空阵列。

我决定尝试使用ArrayList而不是JArray，然后将它传递给序列化程序并且它有效。我不是100％肯定为什么这解决了这个问题，我仍在研究具体原因。

        ArrayList postData = new ArrayList();
        postData.Add(JsonConvert.SerializeObject(request));
        foreach (StudentViewModel student in studentviewmodels)
        {
            postData.Add(JsonConvert.SerializeObject(student));
        }

Post上收到空Json数组

2 个答案: