C# - 我的 ASP.NET MVC 页面总是返回 null 给我的 Z0ECD11C1D7A2874201D148A23BBD7A

Question

I have a client that will send some string data to my web page using JSON, but when I post it, it always returns null for some reason.

Is there anything wrong with my post?

Client:

public async Task TesteAsync(string numeroserie)
{
    try
    {
        var json = Newtonsoft.Json.JsonConvert.SerializeObject(numeroserie);
        var data = new System.Net.Http.StringContent(json, Encoding.UTF8, "application/json");

        var url = "https://localhost:44336/Home/Receive";
        var client = new HttpClient();

        var response = await client.PostAsync(url, data);

        string result = response.Content.ReadAsStringAsync().Result;
        MessageBox.Show(result);
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.ToString());
        return;
    }
}

Server Side:

[System.Web.Http.HttpPost]
public string Receive(string json)
{
    return json;
}

My server is using ASP.NET MVC.

Server side using breakpoint when the request is made

Client side using break when sending

Update: What i want to do in the end is send to my webserver a string and then return it to the client. I have no experience with json so i don't know if it's correct what i did

Answer 1

Look. At first lets check http request.

string url = "YourURL";
string body = JsonConvert.SerializeObject(BodyModel);


HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json")); 
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, url)
{
   Content = new StringContent(body, Encoding.UTF8, "application/json")
};
HttpResponseMessage response = await client.SendAsync(request);
if ((int)response.StatusCode == 200)
{
   string responseString = await response.Content.ReadAsStringAsync();
   ResponseModel responseModel = JsonConvert.DeserializeObject<ResponseModel>(responseString);
}

now lets make some changes in your controller.

[HttpPost]
public JsonResult Receive([FromBody] YourJsonModel parameters)
{
   //Do logic
   return Json(YourResponseModel);
}

Here is the case when you want to pass string and get it as string. In your controller you can use [FromQuery] or just left string both are ok.

[HttpPost]
public string SomeAction(string data) // public string SomeAction([FromQuery] string data)
{
    return data;
}

And here is the request

string url = "http://localhost:15832/YOURCONTROLLERNAME/SomeAction?data=YOURSTRINGVALUE";
HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, url)
{
    Content = new StringContent("", Encoding.UTF8, "application/json")
};
HttpResponseMessage response = await client.SendAsync(request);
if ((int)response.StatusCode == 200)
{
    string responseString = await response.Content.ReadAsStringAsync(); // here is your response as string
}

PS If you are not sending body, you can change action type to HttpGet. As it comfortable to your task.