Develop Reference

ASP.NET Web API post to an external api

I would like to ask if it is possible for a created ASP.NET Web API (written in C#) to post to an external API?
If it is possible, please share sample code that can post to an url with adding headers and receive a callback from the external API.

A simple way to make HTTP-Request out of a .NET-Application is the System.Net.Http.HttpClient (MSDN). An example usage would look something like this:
// Should be a static readonly field/property, wich is only instanciated once
var client = new HttpClient();
var requestData = new Dictionary<string, string>
{
{ "field1", "Some data of the field" },
{ "field2", "Even more data" }
};
var request = new HttpRequestMessage() {
RequestUri = new Uri("https://domain.top/route"),
Method = HttpMethod.Post,
Content = new FormUrlEncodedContent(requestData)
};
request.Headers // Add or modify headers
var response = await client.SendAsync(request);
// To read the response as string
var responseString = await response.Content.ReadAsStringAsync();
// To read the response as json
var responseJson = await response.Content.ReadAsAsync<ResponseObject>();

Essentially you need use an instance of HttpClient to send an HttpRequestMessage to an endpoint.
Here is an example to post some jsonData to someEndPointUrl:
var client = new HttpClient();
var request = new HttpRequestMessage(HttpMethod.Post, someEndPointUrl);
request.Headers.Accept.Clear();
request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
request.Content = new StringContent(jsonData, Encoding.UTF8, "application/json");
var response = await client.SendAsync(request, CancellationToken.None);
var str = await response.Content.ReadAsStringAsync();
if (response.StatusCode == HttpStatusCode.OK)
{
// handle your response
}
else
{
// or failed response ?
}

How to call Rest API with Content and Headers in c#?

I am trying to call Rest API with content and headers in c#. Actually I am trying to convert to c# from Python code which is:
import requests
url = 'http://url.../token'
payload = 'grant_type=password&username=username&password=password'
headers = {
'Content-Type': 'application/x-www-form-urlencoded'
}
response = requests.request('POST', url, headers = headers, data = payload, allow_redirects=False)
print(response.text)
So far I am trying with:
HttpClient client = new HttpClient();
client.BaseAddress = new Uri(Url);
var tmp = new HttpRequestMessage
{
Method = HttpMethod.Post,
Content =
{
}
};
var result = client.PostAsync(Url, tmp.Content).Result;
}
I have no idea how to put from Python code Headers (Content-Type) and additional string (payload).

If you use RestSharp, you should be able to call your service with the following code snipped
var client = new RestClient("http://url.../token");
var request = new RestRequest(Method.POST);
request.AddHeader("content-type", "application/x-www-form-urlencoded");
request.AddParameter("application/x-www-form-urlencoded", "grant_type=password&username=username&password=password", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
var result = response.Content;
I based my answer on the anwser of this answer.

Here a sample I use in one of my apps:
_client = new HttpClient { BaseAddress = new Uri(ConfigManager.Api.BaseUrl),
Timeout = new TimeSpan(0, 0, 0, 0, -1) };
_client.DefaultRequestHeaders.Accept.Clear();
_client.DefaultRequestHeaders.Accept.Add(
new MediaTypeWithQualityHeaderValue("application/json"));
_client.DefaultRequestHeaders.Add("Bearer", "some token goes here");

using System.Net.Http;
var content = new StringContent("grant_type=password&username=username&password=password");
content.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
client.PostAsync(Url, content);
Or use FormUrlEncodedContent without set header
var data = new Dictionary<string, string>
{
{"grant_type", "password"},
{"username", "username"},
{"password", "password"}
};
var content = new FormUrlEncodedContent(data);
client.PostAsync(Url, content);
If you write UWP application, use HttpStringContent or HttpFormUrlEncodedContent instead in Windows.Web.Http.dll.
using Windows.Web.Http;
var content = new HttpStringContent("grant_type=password&username=username&password=password");
content.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
client.PostAsync(Url, content);
var data = new Dictionary<string, string>
{
{"grant_type", "password"},
{"username", "username"},
{"password", "password"}
};
var content = new FormUrlEncodedContent(data);
client.PostAsync(Url, content);

HttpClient post async form-url-encoded and string content not working

I am trying to use System.Net.Http.HttpClient PostAsync method to make an api call. It hangs forever after await _httpClient.PostAsync(requestUri, stringContent);
HttpClient configuration :
_httpClient = new System.Net.Http.HttpClient(new HttpClientHandler
{
UseDefaultCredentials = WithDefaultCredentials,
AllowAutoRedirect = false
});
_httpClient.DefaultRequestHeaders.Accept.Clear();
_httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(APPLICATION_JSON));
_httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(ApplicationXWwwFormUrlencoded));
if (!string.IsNullOrEmpty(CultureInfo.CurrentUICulture.Name))
{
_httpClient.DefaultRequestHeaders.AcceptLanguage.Add(new
StringWithQualityHeaderValue(CultureInfo.CurrentUICulture.Name));
}
PostAsync call :
var stringContent = new StringContent(content);
stringContent.Headers.ContentType = MediaTypeHeaderValue.Parse("application/x-www-form-urlencoded");
var response = await _httpClient.PostAsync(requestUri, stringContent);
var responseContent = await response.Content.ReadAsStringAsync();

Using FormUrlEncodedContent instead of string content fixed my problem :
var requestContent = new FormUrlEncodedContent(new[]
{
new KeyValuePair<string, string>("password", password),
new KeyValuePair<string, string>("username", username),
// ...
});
var response = await _httpClient.PostAsync(requestUri, requestContent);
var responseContent = await response.Content.ReadAsStringAsync();

HttpClient sending parameter null

I'm trying to send data to an api with HttpClient but parameter I'm sending keeps received as 0.
What am I doing wrong here? It's my first usage of HttpClient so it's quite possible I mixed things or made some rookie mistake.
Path is correct, I can get results from Postman.
Code I'm using is this;
static async Task GetActivityList()
{
string uri = "/api/ExtraNet/GetActivityList";
HttpClient client = new HttpClient();
int SalesPersonId = 553;
string token = my token value is here;
client.BaseAddress = new Uri("http://localhost:16513/");
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(
new MediaTypeWithQualityHeaderValue("application/json"));
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
var postData = "{\"SalesPersonId=\":\""+SalesPersonId+"\"}";
var stringContent = new StringContent( "{\"SalesPersonId=\":\"" + SalesPersonId + "\"}", Encoding.UTF8, "application/json") ;
var content = new StringContent(postData, Encoding.UTF8, "application/json");
var response = await client.PostAsync("http://localhost:16513/api/ExtraNet/GetActivityList", stringContent);
var result = await response.Content.ReadAsStringAsync();
Console.WriteLine(result);
}

I managed to send the parameter this way
string uri = "/api/ExtraNet/GetActivityList";
HttpClient client = new HttpClient();
int SalesPersonId = 553;
string token = "";
client.BaseAddress = new Uri("http://localhost:16513/");
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(
new MediaTypeWithQualityHeaderValue("application/json"));
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
var stringContent = new FormUrlEncodedContent(new[] {
new KeyValuePair<string,string>("SalesPersonId","553")
});
var response = await client.PostAsync(uri, stringContent);
var result = await response.Content.ReadAsStringAsync();
Console.WriteLine(result);
Sending the parameters as FormUrlEncodedContent did the trick.

Trustpilot OAuth Restful API: Unable to PostAsync

I am trying to use the Trustpilot API, to post invitations to review products.
I have successfully gone through the authentication step as you can see in the code below, however I am unable to successfully post data to the Trustpilot Invitations API. The PostAsnyc method appears to be stuck with an WaitingForActivation status. I wonder if there is anything you can suggest to help.
Here is my code for this (the API credentials here aren't genuine!):
using (HttpClient httpClient = new HttpClient())
{
string trustPilotAccessTokenUrl = "https://api.trustpilot.com/v1/oauth/oauth-business-users-for-applications/accesstoken";
httpClient.BaseAddress = new Uri(trustPilotAccessTokenUrl);
httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/x-www-form-urlencoded"));
var authString = "MyApiKey:MyApiSecret";
httpClient.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Basic", Base64Encode(authString));
var stringPayload = "grant_type=password&username=MyUserEmail&password=MyPassword";
var httpContent = new StringContent(stringPayload, Encoding.UTF8, "application/x-www-form-urlencoded");
HttpResponseMessage httpResponseMessage = httpClient.PostAsync(trustPilotAccessTokenUrl, httpContent).Result;
var accessTokenResponseString = httpResponseMessage.Content.ReadAsStringAsync().Result;
var accessTokenResponseObject = JsonConvert.DeserializeObject<AccessTokenResponse>(accessTokenResponseString);
// Create invitation object
var invitation = new ReviewInvitation
{
ReferenceID = "inv001",
RecipientName = "Jon Doe",
RecipientEmail = "Jon.Doe#comp.com",
Locale = "en-US"
};
var jsonInvitation = JsonConvert.SerializeObject(invitation);
var client = new HttpClient();
client.DefaultRequestHeaders.Add("token", accessTokenResponseObject.AccessToken);
var invitationsUri = new Uri("https://invitations-api.trustpilot.com/v1/private/business-units/{MyBusinessID}/invitations");
// This here as a status of WaitingForActivation!
var a = client.PostAsync(invitationsUri, new StringContent(jsonInvitation)).ContinueWith((postTask) => postTask.Result.EnsureSuccessStatusCode());
}

This is how I solved the issue:
// Serialize our concrete class into a JSON String
var jsonInvitation = JsonConvert.SerializeObject(invitationObject);
// Wrap our JSON inside a StringContent which then can be used by the HttpClient class
var stringContent = new StringContent(jsonInvitation);
// Get the access token
var token = GetAccessToken().AccessToken;
// Create a Uri
var postUri = new Uri("https://invitations-api.trustpilot.com/v1/private/business-units/{BusinessUnitID}/invitations");
// Set up the request
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, postUri);
request.Content = stringContent;
request.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
request.Content.Headers.Add("token", token);
// Set up the HttpClient
var httpClient = new HttpClient();
//httpClient.DefaultRequestHeaders.Accept.Clear();
//httpClient.BaseAddress = postUri;
//httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
//httpClient.DefaultRequestHeaders.AcceptLanguage.Add(new StringWithQualityHeaderValue("en-US"));
var task = httpClient.SendAsync(request);
task.Wait();
This question here on SO was helpful:
How do you set the Content-Type header for an HttpClient request?