I got a System error in C# post

Question

It is my first time to ask a question in here (I'm from Asia).

Platform：UWP 17632

IDE : Visual Studio 2017

Based on the reqiurement of the project， I need to post some information to a website.

I refer the answer about How to make HTTP POST web request Method A.

Here is my code：

public async void PostDataAsync(string pTemperture, string pHumidity, string pFireStatus, string pLightStatus, string pBodyStatus)
   {
       var values = new Dictionary<string, string>
           {
               {"count", "1" },
               {"temperture_0", pTemperture },
               {"Humidity_0", pHumidity },
               {"FireStatus_0", pFireStatus },
               {"LightStatus_0" ,pLightStatus},
               {"BodyDetect_0", pBodyStatus }
           };
       var content = new FormUrlEncodedContent(values);
       try
       {
           var response = await client.PostAsync("http://115.159.36.210/api/onehome/upload", content);//Here throw an exception
           System.Diagnostics.Debug.WriteLine(response);
           var responseString = response.Content.ReadAsStringAsync();
           System.Diagnostics.Debug.WriteLine(responseString);
       }
       catch (Exception ex)
       {
           System.Diagnostics.Debug.WriteLine(ex.HelpLink);
           System.Diagnostics.Debug.WriteLine(ex.Message);
           throw;
       }            
   }

And then it throws an exception

“An error occurred while sending the request.”

in

var response = await client.PostAsync("http://115.159.36.210/api/onehome/upload", content);

I want to know why and gain the solution which can solve it.
I will be grateful if you can help me.

Look at this link - https://stackoverflow.com/questions/33235131/universal-windows-project-httpclient-exception — Kaushik Srinath, Jun 30 '18 at 10:25
@Kaushik Srinath Thank you!!! I never consider this problem....... — LIFUGUAN, Jul 02 '18 at 12:23

score 2 · Accepted Answer · answered Jul 02 '18 at 08:55

2

It is recommend that use HttpClient and the rest of the Windows.Web.Http namespace API to send and receive information using the HTTP 2.0 and HTTP 1.1 protocols within UWP.

For your requirement, you could make a method to package http POST method like the follow

public async void SendPostMethod(string url, Dictionary<string, string> param, Action<string> response)
{
    HttpClient client = new HttpClient();

    HttpResponseMessage httpResponse = new HttpResponseMessage();
    Uri requestUri = new Uri(url);

    var content = new HttpFormUrlEncodedContent(param);
    try
    {
        httpResponse = await client.PostAsync(requestUri, content);

        response(await httpResponse.Content.ReadAsStringAsync());
    }
    catch (Exception ex)
    {

    }

}

Usage

 this.SendPostMethod("http://115.159.36.210/api/onehome/upload",Param, (res) =>
{

    var response = res;

});

And there are official code sample and document that you could refer.

answered Jul 02 '18 at 08:55

Nico Zhu

32,367
2
15
36

Thank you！I will try it. – LIFUGUAN Jul 02 '18 at 12:27
what exception throw ? – Nico Zhu Jul 03 '18 at 01:47
When I execute the code `httpResponse = await client.PostAsync(requestUri, content);`, it throw an exception: A connection with the server could not be established. And the res is : {"status":-1,"msg":"Error! Invalid Request."} – LIFUGUAN Jul 03 '18 at 02:08
Will it be a problem with the webpage? – LIFUGUAN Jul 03 '18 at 02:09
Yep, you could check the http state code, if the code is 200 that means your request successful. – Nico Zhu Jul 03 '18 at 02:17
Do you miss some token or specified Id parameter ? – Nico Zhu Jul 03 '18 at 02:18
emmmmm， the author of this web didn't finish it.So,,,,,,,it is not the code's fault. – LIFUGUAN Jul 04 '18 at 01:29
Yep, I get the same json in my side. in general, you need add some authentication in your request header. – Nico Zhu Jul 04 '18 at 01:32
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/174301/discussion-between-lifuguan-and-nico-zhu-msft). – LIFUGUAN Jul 04 '18 at 01:38

score 2 · Answer 2 · answered Jul 03 '18 at 15:30

2

I am the author of the server.

The reality is I have not finish the code of the server.

Thus , {"status":-1,"msg":"Error! Invalid Request."} is the default result .....

answered Jul 03 '18 at 15:30

Eric Lian

21
1
3

I got a System error in C# post

2 Answers2