Converting async Task Response to String

Question

First of all, I would like to say, I'm quite new to C#.

I'm trying to create a POST request which sends some data to a PHP file somewhere on a different server.

Now, after the request is send I would like to see the response, as I'm sending back a JSON string from the server as a success message.

When I use the following code:

public MainPage()
{

     this.InitializeComponent();
     Windows.UI.ViewManagement.ApplicationView.GetForCurrentView().SetDesiredBoundsMode(Windows.UI.ViewManagement.ApplicationViewBoundsMode.UseCoreWindow);

     responseBlockTxt.Text = start();
}

public string start()
{
    var response = sendRequest();

    System.Diagnostics.Debug.WriteLine(response);

    return "";
}

public async Task<string> sendRequest()
{
     using (var client = new HttpClient())
     {
          var values = new Dictionary<string, string>
          {
               { "vote", "true" },
               { "slug", "the-slug" }
          };

          var content = new FormUrlEncodedContent(values);

          var response = await client.PostAsync("URL/api.php", content);

          var responseString = await response.Content.ReadAsStringAsync();

          return responseString;
      }

}

The output is:

System.Threading.Tasks.Task`1[System.String]

So, how would I see all the results from this?

@MaksimSimkin results in the following error: An exception of type 'System.AggregateException' occurred in mscorlib.ni.dll but was not handled in user code — Chris
– Chris, Commented Jan 15, 2017 at 13:39
@Chris Don't mix async and blocking calls (.Result, .Wait()) you may get deadlocks. Go async all the way. Read up here msdn.microsoft.com/en-us/magazine/jj991977.aspx — Nkosi
– Nkosi, Commented Jan 15, 2017 at 13:46
@Nkosi like this for now: responseBlockTxt.Text = start(); — Chris
– Chris, Commented Jan 15, 2017 at 13:53

Nkosi · Accepted Answer · 2019-02-01 13:57:06Z

4

Go Async all the way. Avoid blocking calls when calling async methods. async void is allowed in event handlers so update page to perform the call on load event

Read up on Async/Await - Best Practices in Asynchronous Programming

And then update your code accordingly

public MainPage() {    
    this.InitializeComponent();
    Windows.UI.ViewManagement.ApplicationView.GetForCurrentView().SetDesiredBoundsMode(Windows.UI.ViewManagement.ApplicationViewBoundsMode.UseCoreWindow);
    this.Loaded += OnLoaded;     
}

public async void OnLoaded(object sender, RoutedEventArgs e) {
    responseBlockTxt.Text = await start();
}

public async Task<string> start() {
    var response = await sendRequest();

    System.Diagnostics.Debug.WriteLine(response);

    return response;
}

private static HttpClient client = new HttpClient();

public async Task<string> sendRequest() {
    var values = new Dictionary<string, string> {
        { "vote", "true" },
        { "slug", "the-slug" }
    };

    var content = new FormUrlEncodedContent(values);
    using(var response = await client.PostAsync("URL/api.php", content)) {
        var responseString = await response.Content.ReadAsStringAsync();
        return responseString;
    }
}

edited Feb 1, 2019 at 13:57

answered Jan 15, 2017 at 13:59

Nkosi

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2 Comments

Chris Over a year ago

Alright, we're going in the right direction. The only error that pops-up now is at this.Loaded += OnLoad;. Error: No overload for 'OnLoad' matches delegate 'RoutedEventHandler'

Nkosi Over a year ago

@Chris, that was a typo on my part. Change EventArg to RoutedEventArgs. Will update answer to fix typo.

Community · Accepted Answer · 2017-05-23 11:53:26Z

1

The problem is in the start method, the SendRequest method returns a Task<string> and that's what you get on your response variable. Since you are attempting to run an async method synchronously you have to do some extra stuff, try this:

public string start()
{
    var response = sendRequest().ConfigureAwait(true)
                                .GetAwaiter()
                                .GetResult();

    System.Diagnostics.Debug.WriteLine(response);

    return "";
}

That get the actual result inside your awaitable Task<string>. If you want to find some more info on this take a look at this question

edited May 23, 2017 at 11:53

CommunityBot

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answered Jan 15, 2017 at 13:42

Luiso

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4 Comments

Chris Over a year ago

Hey @Luiso. Thanks for the answer. Unfortunately, the following error pops-up now: An exception of type 'System.Net.Http.HttpRequestException' occurred in mscorlib.ni.dll but was not handled in user code

Luiso Over a year ago

That means there is something wrong with your request, you had an issue with concurrency now you have one with the request, please update your question and add as much data as you can so we can improve on that

Chris Over a year ago

What I'm showing is pretty much all I have. The url I'm using is working just fine. I'm used to use it in AJAX. Now trying to use the same thing in here.

Luiso Over a year ago

I think you should take a look at what the actual Exception looks like. With what you're giving us we can only tell there is something wrong with the request, and not what went wrong with it

Stilet · Accepted Answer · 2017-01-15 13:46:18Z

1

I Guess

public string start()
{
    var response = sendRequest();
    Task<String> t = sendRequest();
    System.Diagnostics.Debug.WriteLine(t.Result);

    return "";
}

public async Task<string> sendRequest()
{
     using (var client = new HttpClient())
     {
          var values = new Dictionary<string, string>
          {
               { "vote", "true" },
               { "slug", "the-slug" }
          };

          var content = new FormUrlEncodedContent(values);

          var response = await client.PostAsync("URL/api.php", content);

          var responseString = await response.Content.ReadAsStringAsync();

          return responseString;
      }

}

answered Jan 15, 2017 at 13:46

Stilet

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Comments

Kamal Panhwar · Accepted Answer · 2019-04-26 11:57:00Z

0

public string start()
  {
    var response = sendRequest().ConfigureAwait(true)
                                .GetAwaiter()
                                .GetResult();

    System.Diagnostics.Debug.WriteLine(response);
    return "";
   }

I have Tried this. It is working perfectly.

edited Apr 26, 2019 at 11:57

Kamal Panhwar

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answered Apr 26, 2019 at 11:22

Ahmer Khan

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