HttpClient PostAsync() not working in Xamarin Forms App

Question

In my Xamarin Forms App

I'm trying to Post a JSON String to my webservice which is RestFul API when I use the following code:

public static async Task<bool> SaveRolAsync(Methods Method, Role Rol)
    {
        try
        {
            HttpClient client = new HttpClient();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

            var uri = ("http://myservice.com/roles/");
            HttpResponseMessage response = null;

            try
            {
                var jSettings = new JsonSerializerSettings();
                jSettings.NullValueHandling = NullValueHandling.Ignore;
                jSettings.MissingMemberHandling = MissingMemberHandling.Ignore;

                var JsonData = JsonConvert.SerializeObject(Rol);
                var RoleContent = new StringContent(JsonData, Encoding.UTF8, "application/json");

                if (Method == Methods.PUT || Method == Methods.PATCH)
                {
                    response = await client.PutAsync(uri, RoleContent);
                }

                if (Method == Methods.POST)
                {
                    response = await client.PostAsync(uri, RoleContent);
                }

                if (Method == Methods.DELETE)
                {
                    throw new NotImplementedException();
                }

                return response.IsSuccessStatusCode;

            }
            catch (JsonException jse)
            {
                return false;
            }
        }
        catch (Exception ex)
        {
            // Exceptions Throws here
            // @T This line I got The request requires buffering data to succeed
            return false;
        }
    }

The Exception throws:

The request requires buffering data to succeed

Stack Trace:

{System.Net.WebException: The request requires buffering data to succeed. at System.Net.HttpWebRequest.EndGetResponse (System.IAsyncResult asyncResult) [0x00064] in :0 at System.Threading.Tasks.TaskFactory1[TResult].FromAsyncCoreLogic (System.IAsyncResult iar, System.Func2[T,TResult] endFunction, System.Action1[T] endAction, System.Threading.Tasks.Task1[TResult] promise, System.Boolean requiresSynchronization) [0x00014] in :0 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in :0 at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0004e] in :0 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in :0 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in :0 at System.Runtime.CompilerServices.ConfiguredTaskAwaitable1+ConfiguredTaskAwaiter[TResult].GetResult () [0x00000] in <a66f207c1e5949e9a252c01e27bbd34e>:0 at System.Net.Http.HttpClientHandler+<SendAsync>c__async0.MoveNext () [0x0041e] in <566d6cf6576345098cb5e08ad43d5e78>:0 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in <a66f207c1e5949e9a252c01e27bbd34e>:0 at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0004e] in <a66f207c1e5949e9a252c01e27bbd34e>:0 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in <a66f207c1e5949e9a252c01e27bbd34e>:0 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in <a66f207c1e5949e9a252c01e27bbd34e>:0 at System.Runtime.CompilerServices.ConfiguredTaskAwaitable1+ConfiguredTaskAwaiter[TResult].GetResult () [0x00000] in :0 at System.Net.Http.HttpClient+c__async0.MoveNext () [0x000f3] in <566d6cf6576345098cb5e08ad43d5e78>:0 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in :0 at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0004e] in :0 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in :0 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in :0 at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in :0 at MyAPP.Webservice+d__4.MoveNext () [0x000d0] in C:\MyProject\Classes\Webservice.cs:140 }

**Also Tried: SendAsync() Ty M. Wiśnicki **

public static async Task<bool> SaveRolAsync(MediwareLib.Methods Method, Role Rol)
    {
        try
        {
            HttpClient client = new HttpClient();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

            var uri = (BaseRequestUrl + "roles/");
            HttpResponseMessage response = null;
            var request = new HttpRequestMessage();

            try
            {
                var jSettings = new JsonSerializerSettings();
                jSettings.NullValueHandling = NullValueHandling.Ignore;
                jSettings.MissingMemberHandling = MissingMemberHandling.Ignore;

                var JsonData = JsonConvert.SerializeObject(Rol);

                var RoleContent = new StringContent(JsonData, Encoding.UTF8, "application/json");

                if (Method == MediwareLib.Methods.PUT || Method == MediwareLib.Methods.PATCH)
                {
                    request = new HttpRequestMessage(HttpMethod.Put, uri);
                    request.Content = RoleContent;

                    response = await client.SendAsync(request,
                    HttpCompletionOption.ResponseHeadersRead);
                }

                if (Method == MediwareLib.Methods.POST)
                {
                    request = new HttpRequestMessage(HttpMethod.Post, uri);
                    request.Content = RoleContent;

                    response = await client.SendAsync(request,
                    HttpCompletionOption.ResponseHeadersRead);
                }

                if (Method == MediwareLib.Methods.DELETE)
                {
                    throw new NotImplementedException();
                    // response = await client.DeleteAsync(uri + Rol.Id);
                }

                return response.IsSuccessStatusCode;

            }
            catch (JsonException jse)
            {
                Globals.Log("SaveRolAsync: " + jse.ToString());
                return false;
            }
        }
        catch (Exception ex)
        {
            Globals.Log("SaveRolAsync: " + ex.ToString());
            return false;
        }

    }

So what did your research show? Did you read The request requires buffering data to succeed HttpClient and Head request with HttpClient? Did you notice you're sending a PUT even if (Method == Methods.POST)? Is your service responding with a redirect? — CodeCaster
– CodeCaster, Commented Dec 22, 2016 at 12:14
Ofc i did read other stackoverflow posts but i want to send a json string not a google request. — Stefan van de Laarschot
– Stefan van de Laarschot, Commented Dec 22, 2016 at 13:32
An HTTP request is an HTTP request, whether it contains search results or JSON data. — CodeCaster
– CodeCaster, Commented Dec 22, 2016 at 13:37
Would be nice to know in which line the exception is thrown :) — Dennis Schröer
– Dennis Schröer, Commented Dec 22, 2016 at 14:23

Hasan Fathi · Accepted Answer · 2018-01-20 14:09:54Z

10

Since you are using .Result or .Wait or await this will end up causing a deadlock in your code.

you can use ConfigureAwait(false) in async methods for preventing deadlock

like this:

response = await client.PostAsync(uri, RoleContent).ConfigureAwait(false);

you can use ConfigureAwait(false) wherever possible for Don't Block Async Code .

answered Jan 20, 2018 at 14:09

Hasan Fathi

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Comments

M. Wiśnicki · Accepted Answer · 2016-12-27 10:13:47Z

3

You can use SendAsync() with HttpCompletionOption.ResponseHeadersRead instead PostAsync(), the problem is with reading response, it's reading when it not ready.

var request = new HttpMessageRequest(yourUrl);
request.Content = yourContent;
var response = await client.SendAsync(request, 
HttpCompletionOption.ResponseHeadersRead);

Using HttpCompletionOption.ResponseHeadersRead

The operation should complete as soon as a response is available and headers are read. The content is not read yet.

Edit You can use HttpWebRequest instead HttpClient

   public async Task<string> PostTest(object sampleData, string uri)
    {
        var request = (HttpWebRequest) WebRequest.Create(new Uri(uri));
        request.ContentType = "application/json";
        request.Method = "POST";
        request.Timeout = 4000; //ms
        var itemToSend = JsonConvert.SerializeObject(sampleData);
        using (var streamWriter = new StreamWriter(await request.GetRequestStreamAsync()))
        {
            streamWriter.Write(itemToSend);
            streamWriter.Flush();
            streamWriter.Dispose();
        }

        // Send the request to the server and wait for the response:  
        using (var response = await request.GetResponseAsync())
        {
            // Get a stream representation of the HTTP web response:  
            using (var stream = response.GetResponseStream())
            {
                var reader = new StreamReader(stream);
                var message = reader.ReadToEnd();
                return message;
            }
        }
    }

edited Dec 27, 2016 at 10:13

answered Dec 27, 2016 at 9:11

M. Wiśnicki

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7 Comments

Stefan van de Laarschot Over a year ago

Same error :( System.Net.WebException: The request requires buffering data to succeed.

M. Wiśnicki Over a year ago

@StefanvandeLaarschot You using new HttpRequestMessage(HttpMethod.Post, uri); but i wrote without HttpMethod, use with uri only.

Stefan van de Laarschot Over a year ago

It can't it expects HttpMethod, uri or String as Uri

Stefan van de Laarschot Over a year ago

Same: System.Net.WebException: The request requires buffering data to succeed.

M. Wiśnicki Over a year ago

I think the problem is with try catch block. Be sure you not block on async code. Also try run post with client.PostAsync(uri, RoleContent).Result; without await.Here you find article why cant block async blog.stephencleary.com/2012/07/dont-block-on-async-code.html

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