Develop Reference

Xamarin Sending POST Data

I am attempting to send POST data to my server and get back a response. For some reason, no POST data is actually getting sent. A request is being sent to my server but the POST array is empty.
Here is my code for sending the request:
public class GlobalMethods
{
public async Task<string> callAjax(string mthd,NameValueCollection parameters)
{
var client = new HttpClient();
var content = JsonConvert.SerializeObject(parameters);
var result = await client.PostAsync("http://dev.adex-intl.com/adex/mvc/receiving/"+mthd, new StringContent(content)).ConfigureAwait(false);
var tokenJson = "";
if (result.IsSuccessStatusCode)
{
tokenJson = await result.Content.ReadAsStringAsync();
}
return tokenJson;
}
}
And here is my code that calls the above method:
public void loginPressed(object sender, EventArgs e)
{
if(String.IsNullOrEmpty(badge.Text)) {
DisplayAlert("Error", "Enter your badge number", "Ok");
} else {
IsBusy = true;
NameValueCollection parameters = new NameValueCollection();
parameters["badgetNumber"] = badge.Text;
GlobalMethods globalMethods = new GlobalMethods();
var results = globalMethods.callAjax("login", parameters);
}
}
I'm not sure what I'm doing wrong. Also, I'm a newbie to Xamarin and C# so I'm not even sure if the way I am attempting to do things is the best way.

You haven't specify the type of content that you want to send, in your case it's 'application/json', you can set it like that:
"var client = new HttpClient();
var content = new StringContent(JsonConvert.SerializeObject(parameters));
content.Headers.ContentType = new MediaTypeHeaderValue("application/json");". Also, I would suggest you to write code like that:
var uri = new Uri(url);
using (var body = new StringContent(JsonConvert.SerializeObject(data)))
{
body.Headers.ContentType = new MediaTypeHeaderValue("application/json");
var request = new HttpRequestMessage
{
Version = new Version(1, 0),
Content = body,
Method = HttpMethod.Post,
RequestUri = uri
};
try
{
using (var response = await _client.SendAsync(request,cancellationToken))
{
if (response.IsSuccessStatusCode)
{
//Deal with success response
}
else
{
//Deal with non-success response
}
}
}
catch(Exception ex)
{
//Deal with exception.
}
}

You can use PostAsync for async sending data to server. your code should be something like this:
HttpClient client = new HttpClient();
var values = new Dictionary<string, string>
{
{ "p1", "data1" },
{ "p2", "data2" }
};
var content = new FormUrlEncodedContent(values);
var response = await client.PostAsync("http://www.example.com/index.php", content);
var responseString = await response.Content.ReadAsStringAsync();

Xamarin Forms Json Service Insert Data

I want to add a record to the json service in my application. How can I do this via Service Url. Here is my code.
CustomerModel customer = new CustomerModel();
customer.Name = entryCompanyName.Text;
customer.Title = entryCompanyTitle.Text;
customer.PhoneNumber = entryTelephone.Text;
customer.FaxNumber = entryFax.Text;
customer.Email = entryEmail.Text;
customer.CityId = 6444;
string json = JsonConvert.SerializeObject(customer);
string sContentType = "application/json";
string path = "service url";
HttpClient Client = new HttpClient();
var task = Client.PostAsync(path, new StringContent(json.ToString(), Encoding.UTF8, sContentType));
I'm trying M. Wiśnicki's solution, but I took this error
I did not get an error when I added System.net :( Where do i make mistakes?

This worked for me
public static async Task<string> PostEntityToApi<T>(string yourMethodUrl, T yourModel)
{
try
{
if (_httpClient == null)
{
_httpClient = new HttpClient { BaseAddress = new Uri(yourWebSiteUrl) };
}
var stringContentInput = new StringContent(JsonConvert.SerializeObject(dto), Encoding.UTF8, "application/json");
var response = await _httpClient.PostAsync(new Uri(yourWebSiteUrl. + apiUrl), stringContentInput);
if (!response.IsSuccessStatusCode)
{
throw new Exception(response.StatusCode.ToString());
}
var stringAsync = await response.Content.ReadAsStringAsync();
LoggingManager.Error("Received error response: " + stringAsync);
return stringAsync;
}
catch (Exception exception)
{
return null;
}
}

You can use WebRequest, this sample working for me, i use it in my app.
This is System.Net.WebRequest class, here you find doc.
public async Task<string> PostSample(object data, string uri)
{
// Create an HTTP web request using the URL:
var request = (HttpWebRequest) WebRequest.Create(new Uri(uri));
request.ContentType = "application/json";
request.Method = "POST";
var itemToSend = JsonConvert.SerializeObject(data);
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 = JsonConvert.DeserializeObject<string>(reader.ReadToEnd());
return message;
}
}
}

System.Net.Http.HttpClient in [Universal Windows Platform] not working properly

I wrote simple method for getting data from (online) REST Service:
public async Task<Object> GetTask()
{
try
{
using (HttpClient client = new HttpClient())
{
client.BaseAddress = new Uri("http://111.111.111.111:8080/");
HttpResponseMessage result = await client.GetAsync("ABC/CDE/getsomeinfo");
if (result.IsSuccessStatusCode)
{
//Deserialize
}
}
}
catch (Exception ex)
{
Debug.WriteLine("Error" + ex);
}
return null;
}
Whenever i run this on UWP i'm getting catch exception:
The text associated with this error code could not be found.
A connection with the server could not be established
HResult 2147012867
Im trying to connect my client with restapi in internal network. In forms same code is working properly.

Try this
HttpResponseMessage response;
public async Task<string> webserviceResponse(string HttpMethod)
{
// check internet connection is available or not
if (NetworkInterface.GetIsNetworkAvailable() == true)
{
// CancellationTokenSource cts = new CancellationTokenSource(2000); // 2 seconds
HttpClient client = new HttpClient();
MultipartFormDataContent mfdc = new MultipartFormDataContent();
mfdc.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data");
string GenrateUrl = "your url";
if (HttpMethod == "POST")
{
response = await client.PostAsync(GenrateUrl, mfdc);
}
else if (HttpMethod == "PUT")
{
response = await client.PutAsync(GenrateUrl, mfdc);
}
else if (HttpMethod == "GET")
{
response = await client.GetAsync(GenrateUrl);
}
var respon = await response.Content.ReadAsStringAsync();
string convert_response = respon.ToString();
return convert_response;
}
else
{
return "0";
}
}

Paypal Rest Api With RestSharp not working in xamarin android

I have got error with RestSharp component when i am call Paypal Rest API.
I have the following code using Xamarin for Android.
public async Task<PayPalGetTokenResponse> GetAccessToken()
{
var restRequest = new RestRequest("/oauth2/token", Method.POST);
// Add headers
restRequest.AddHeader("Accept", "application/json");
restRequest.AddHeader("Accept-Language", "en_US");
// Make Authorization header
restClient.Authenticator = new HttpBasicAuthenticator(Config.ApiClientId, Config.ApiSecret);
// add data to send
restRequest.AddParameter("grant_type", "client_credentials");
var response = restClient.Execute<PayPalGetTokenResponse>(restRequest);
response.Data.DisplayError = CheckResponseStatus(response, HttpStatusCode.OK);
return response.Data;
}
But got error :"Error: SecureChannelFailure (The authentication or decryption has failed.)"
I have Also use ModernHttpClient but got same error
public async Task<PayPalGetTokenResponse> GetAccessToken()
{
string clientId = Config.ApiClientId;
string secret = Config.ApiSecret;
string oAuthCredentials = Convert.ToBase64String(Encoding.Default.GetBytes(clientId + ":" + secret));
string uriString = Config.ApiUrl+"/oauth2/token";
PayPalGetTokenResponse result;
HttpClient client = new HttpClient(new NativeMessageHandler());
var h_request = new HttpRequestMessage(HttpMethod.Post, uriString);
h_request.Headers.Authorization = new AuthenticationHeaderValue("Basic", oAuthCredentials);
h_request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
h_request.Headers.AcceptLanguage.Add(new StringWithQualityHeaderValue("en_US"));
h_request.Content = new StringContent("grant_type=client_credentials", UTF8Encoding.UTF8);
try
{
HttpResponseMessage response = await client.SendAsync(h_request);
//if call failed ErrorResponse created...simple class with response properties
if (!response.IsSuccessStatusCode)
{
var error = await response.Content.ReadAsStringAsync();
var errResp = JsonConvert.DeserializeObject<string>(error);
//throw new PayPalException { error_name = errResp.name, details = errResp.details, message = errResp.message };
}
var success = await response.Content.ReadAsStringAsync();
result = JsonConvert.DeserializeObject<PayPalGetTokenResponse>(success);
}
catch (Exception)
{
throw new HttpRequestException("Request to PayPal Service failed.");
}
return result;
}

Have you tried to force to modern day SSL protocol?
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
This works for me:
if (ServicePointManager.SecurityProtocol != SecurityProtocolType.Tls12)
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
var client = new RestClient(payPalURL) {
Encoding = Encoding.UTF8
};
var authRequest = new RestRequest("oauth2/token", Method.POST) {
RequestFormat = DataFormat.Json
};
client.Authenticator = new HttpBasicAuthenticator(clientId, secret);
authRequest.AddParameter("grant_type","client_credentials");
var authResponse = client.Execute(authRequest);

C# Xamarin Android Rest call in PCL error "Unexpected character encountered while parsing value: S. Path '', line 0, position 0."

I have used SO to help with several issues in the past. However, I cannot find a solution to something I have been struggling with for 2 days now.
I am a noob, please be kind :)
I have an app that I created using Xamarin Studio, targeted for Android. It is a basic GET request from a Rest Api. It was working perfectly until I realized I was not helping myself when it came time to create the same app in IOS and Windows. Once I changed my project to utilize a PCL I started getting errors, primarily around my RestClient class (originally got from http://www.codeproject.com/Tips/497123/How-to-make-REST-requests-with-Csharp)
From my droid app class:
var apiUser = GetString(Resource.String.apiUser);
var apiPass = GetString(Resource.String.apiPass);
//Get token from API
string token = authenticate(apiUser,apiPass);
public static string authenticate(string apiUser, string apiPass)
{
Authentication Auth = new Authentication ();
try
{
// set json by passing AuthenticationUrl as endpoint, returns json data
var o = JObject.Parse(EntryRepository.getJson(PJTApiUrls.getAuthenticationUrl(apiUser,apiPass)));
Auth.Token = (string)o["Token"];
return Auth.Token;
}
catch (Exception e)
{
// Couldn't do stuff. Log the exception.
// TODO possible timeout, try again, if fails again then return error message
if (e.Message.Contains("400") || e.Message.Contains("401"))
{
string error = string.Format("Invalid credentials, please try again");
return error;
} else {
string error = string.Format ("An error occurred: \r\n{0}", e.Message);
return error;
}
}
}
getAuthenticationUrl gets the api URL.
Here is getJson (in PCL):
public static string getJson(string endpoint)
{
string apiurl = endpoint;
var client = new _RestClient();
client.EndPoint = apiurl;
client.ContentType = "application/json";
client.Method = HttpVerb.GET;
//client.Method = HttpVerb.POST;
client.PostData = "";
//client.PostData = "{postData: value}";
//client.PostData = "{'someValueToPost': 'The Value being Posted'}";
var json = client._MakeRequestAsync();
// to append parameters, pass them into make request:
//var json = client.MakeRequest("?param=0");
return json.ToString();
}
And for the _RestClient class (in PCL):
public async Task<string> _MakeRequestAsync()
{
try {
var request = _MakeRequestAsync ("");
return await request;
}
catch (Exception e){
return e.Message;
}
}
public async Task<string> _MakeRequestAsync(string parameters)
{
var uri = new Uri(EndPoint + parameters);
var request = WebRequest.Create(uri) as HttpWebRequest;
using (var response = await request.GetResponseAsync () as HttpWebResponse) {
var responseValue = string.Empty;
if (response.StatusCode != HttpStatusCode.OK) {
var message = String.Format ("Request failed. Received HTTP {0}", response.StatusCode);
throw new Exception (message);
}
// grab the response
using (var responseStream = await Task.Factory.FromAsync<Stream>(request.BeginGetRequestStream, request.EndGetRequestStream, null)) {
//using (var responseStream = response.GetResponseStream ()) {
if (responseStream != null)
using (var reader = new StreamReader (responseStream)) {
responseValue = reader.ReadToEnd ();
}
}
return responseValue;
}
}
responseValue is returning null
return await request is saying "Status = Waiting for activation"
I have also had the error: "Unexpected character encountered while parsing value: S. Path '', line 0, position 0."
But this works if the RestClient class is within Droid (Instead of the shared PCL) and contains the following:
public string MakeRequest ()
{
return MakeRequest ("");
}
public string MakeRequest (string parameters)
{
var request = (HttpWebRequest)WebRequest.Create (EndPoint + parameters);
request.Method = Method.ToString ();
request.ContentLength = 0;
request.ContentType = ContentType;
if (!string.IsNullOrEmpty (PostData) && Method == HttpVerb.POST) {
var bytes = Encoding.GetEncoding ("iso-8859-1").GetBytes (PostData);
request.ContentLength = bytes.Length;
using (var writeStream = request.GetRequestStream ()) {
writeStream.Write (bytes, 0, bytes.Length);
}
}
using (var response = (HttpWebResponse)request.GetResponse ()) {
var responseValue = string.Empty;
if (response.StatusCode != HttpStatusCode.OK) {
var message = String.Format ("Request failed. Received HTTP {0}", response.StatusCode);
throw new ApplicationException (message);
}
// grab the response
using (var responseStream = response.GetResponseStream ()) {
if (responseStream != null)
using (var reader = new StreamReader (responseStream)) {
responseValue = reader.ReadToEnd ();
}
}
return responseValue;
}
}
I cannot figure this out, any help/guidance is appreciated. Let me know if I can clarify anything.
***** UPDATE ***** Thanks to #milen-pavlov help thus far, here is where I am currently at:
in Android project:
var apiUser = GetString(Resource.String.apiUser);
var apiPass = GetString(Resource.String.apiPass);
//Get token from API
var token = await authenticate(apiUser,apiPass);
lblOutput.Text = token;
calls (also in Android project):
public static async Task<string> authenticate(string apiUser, string apiPass)
{
Authentication Auth = new Authentication ();
try
{
// set json by passing AuthenticationUrl as endpoint, returns json data
var o = JObject.Parse(await EntryRepository.getJson(PJTApiUrls.getAuthenticationUrl(apiUser,apiPass)));
Auth.Token = (string)o["Token"];
return Auth.Token;
}
catch (Exception e)
{
if (e.Message.Contains("400") || e.Message.Contains("401"))
{
string error = string.Format("Invalid credentials, please try again");
return error;
} else {
string error = string.Format ("An error occurred: \r\n{0}", e.Message);
return error;
}
}
}
Calls json class in PCL project:
public static async Task<string> getJson(string endpoint)
{
string apiurl = endpoint;
var client = new _RestClient();
client.EndPoint = apiurl;
client.ContentType = "application/json";
client.Method = HttpVerb.GET;
client.PostData = "";
var json = await client._MakeRequestAsync();
return json;
}
which then calls restclient class in PCL project:
public async Task<string> _MakeRequestAsync()
{
var request = _MakeRequestAsync ("");
return await request;
}
public async Task<string> _MakeRequestAsync(string parameters)
{
var uri = new Uri(EndPoint + parameters);
using (var client = new HttpClient())
{
var response = await client.GetAsync(uri);
return await response.Content.ReadAsAsync<string>();
};
}
End result/error:
Any guidance is appreciated!

Can you use HttpClient instead?
Sample Get request will look similar to this:
public async Task<string> _MakeRequestAsync(string parameters)
{
var uri = new Uri(EndPoint + parameters);
using (var client = new HttpClient())
{
var response = await client.GetAsync(uri);
return await result.Content.ReadAsStringAsync();
};
}