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C# .NET Core 3.1 Web API Post parameter is Null

I am trying to make a post request from WPF to Web API using the following code but the request parameter is always null.
Request Model
public class Document
{
public string FileName { get; set; }
public byte[] Buffer { get; set; }
}
public class Request
{
public string Uploader { get; set; }
public List<Document> Documents { get; set; }
}
WPF Client
var obj = new Request()
{
Uploader = "John Doe",
Documents = new List<Document>
{
new Document()
{
FileName ="I Love Coding.pdf",
Buffer = System.IO.File.ReadAllBytes(#"C:\Users\john.doe\Downloads\I Love Coding.pdf.pdf")
}
}
};
using (var http = new HttpClient())
{
var encodedJson = JsonConvert.SerializeObject(obj);
var conent = new StringContent(encodedJson, Encoding.UTF8, "application/json");
HttpResponseMessage response = await http.PostAsync("https://my-app.com/api/upload", conent);
response.EnsureSuccessStatusCode();
}
Web API
[Route("")]
public class AppController : ControllerBase
{
[HttpPost]
[Route("api/upload")]
public async Task<IActionResult> UploadDocumentsAsync([FromBody] Request request)
{
// request is always null when app is running in production
// https://my-app.com/api/upload
//request is not null when running on https://localhost:8080/api/upload
}
}
Please what am I missing in the above implementation?
The request parameter is not null on localhost but always null in production.

Please what am I missing in the above implementation? The request
parameter is not null on localhost but always null in production.
Well, not sure how are getting data on local server becuse, you are sending MultipartFormData means your POCO object and file buffer. As you may know we can send json object in FromBody but not the files as json. Thus, I am not sure how it working in local and getting null data is logical in IIS Or Azure.
what am I missing in the above implementation?
As explained above, for sending both POCO object and Files as byte or steam we need to use FromForm and beside that, we need to bind our request object as MultipartFormDataContent to resolve your null data on your UploadDocumentsAsync API action.
Required Change For Solution:
WPF:
In your WPF http request please update your request code snippet as following:
var obj = new Request()
{
Uploader = "John Doe",
Documents = new List<Document>
{
new Document()
{
FileName ="I Love Coding.pdf",
Buffer = System.IO.File.ReadAllBytes(#"YourFilePath")
}
}
};
var httpClient = new HttpClient
{
BaseAddress = new("https://YourServerURL")
};
var formContent = new MultipartFormDataContent();
formContent.Add(new StringContent(obj.Uploader), "Uploader");
formContent.Add(new StringContent(obj.Documents[0].FileName), "Documents[0].FileName");
formContent.Add(new StreamContent(new MemoryStream(obj.Documents[0].Buffer)), "Documents[0].Buffer", obj.Documents[0].FileName);
var response = await httpClient.PostAsync("/api/upload", formContent);
if (response.IsSuccessStatusCode)
{
var responseFromAzureIIS = await response.Content.ReadAsStringAsync();
}
Note: Class in WPF side would remain same as before. No changes required.
Asp.net Core Web API:
In asp.net core web API side you should use [FromForm] instead of [FromBody]
So your controller Action would as following:
[Route("")]
public class AppController : ControllerBase
{
[HttpPost]
[Route("api/upload")]
public async Task<IActionResult> UploadDocumentsAsync([FromForm] Request file)
{
if (file.Documents[0].Buffer == null)
{
return Ok("Null File");
}
return Ok("File Received");
}
}
Note: For remote debugging I have checked the logs and for double check I have used a simple conditionals whether file.Documents[0].Buffer == null. I have tested both in local, IIS and Azure and working accordingly.
Update POCO Class in API Project:
For buffer you have used byte for your WPF project but for Web API project update that to IFormFile instead of byte. It should be as following:
public class Document
{
public string FileName { get; set; }
public IFormFile Buffer { get; set; }
}
public class Request
{
public string Uploader { get; set; }
public List<Document> Documents { get; set; }
}
Output:
If you would like to know more details on it you could check our official document here

How to add below request body (string) in Postman using http client?

Postman Post call Screenshot
Hi Below is my current code:
var url = "https://localhost:44332/token";
var login = new Login()
{
username = "test#gmail.com",
password = "Password#1",
grant_type = "password"
};
using (var client = new HttpClient())
{
httpResponseMessage = await client.PostAsJsonAsync(url, login);
if (httpResponseMessage.IsSuccessStatusCode)
{
var token = httpResponseMessage.Content.ReadAsStringAsync();
}
}
My error is that 400: Bad Request, whenever i make the API call.
If i use postman, its working,
The following is what i put in POSTMAN body:
"username=test#gmail.com&password=Password#1&grant_type=password"
Many Thanks in advance if anyone can correct me!

It looks like you're trying to get hte token from OAuth 2.0 authentications server. You shouldn't be posting JSON - it expects the data as form. It returns a JSON object with access token storen in property access_token - you probably will need to deserialize it as well.
using System.Net.Http.Json;
using System.Text.Json.Serialization;
var url = "https://localhost:44332/token";
var form = new Dictionary<string, string>
{
{"grant_type", "password"},
{"username","test#gmail.com#1"},
{"password", "Password#1"},
};
using (var client = new HttpClient())
{
var response = await client.PostAsync(url, new FormUrlEncodedContent(form));
if (response.IsSuccessStatusCode)
{
var token = await response.Content.ReadFromJsonAsync<Token>();
var accessToken = token.AccessToken;
}
}
class Token
{
[JsonPropertyName("access_token")]
public string AccessToken { get; set; }
[JsonPropertyName("token_type")]
public string TokenType { get; set; }
[JsonPropertyName("expires_in")]
public int ExpiresIn { get; set; }
[JsonPropertyName("refresh_token")]
public string RefreshToken { get; set; }
}

Do you pass these parameters by URL in postman? This form username=test#gmail.com&password=Password#1&grant_type=password looks like you use URL past parameters in postman.
Usually, in POST requests we pass parameters in the request body, not the URL.
Besides, a recommendation is not directly a HttpClient instance. If you use .NET Framework and create the HttpClient instance directly, cannot release the socket resource even if you disposable the HttpClient object. If you use .NET Core, you can inject an HttpClient or IHttpClientFactory.
Refers: Use IHttpClientFactory to implement resilient HTTP requests

SSL/TSL issue when attempting to post message from C# to Slack

I am attempting to post a message using web hooks through Slack in ASP.NET MVC C#. I am getting a SSL/TLS issue when attempting to execute. My code looks great, and I've compared it to several tutorials out there without finding any differences. Here is my SlackClient.cs :
public class SlackClient
{
private readonly Uri _uri;
private readonly Encoding _encoding = new UTF8Encoding();
public SlackClient(string urlWithAccessToken)
{
_uri = new Uri(urlWithAccessToken);
}
//Post a message using simple strings
public void PostMessage(string text, string username = null, string channel = null)
{
Payload payload = new Payload()
{
Channel = channel,
Username = username,
Text = text
};
PostMessage(payload);
}
public HttpResponseMessage PostMessage(Payload payload)
{
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;
string payloadJson = JsonConvert.SerializeObject(payload);
var content = new StringContent(payloadJson, Encoding.UTF8, "application/json");
using (HttpClient client = new HttpClient())
{ var result = client.PostAsync(_uri, content).Result; return result; }
}
}
//This class serializes into the Json payload required by Slack Incoming WebHooks
public class Payload
{
[JsonProperty("channel")]
public string Channel { get; set; }
[JsonProperty("username")]
public string Username { get; set; }
[JsonProperty("text")]
public string Text { get; set; }
}
And here is where I actually call the PostMessage (I've hidden by actual webhook address/token for security purposes)
public void SlackMessageTest()
{
string WebHookUrl = "https://myslackwebsite.slack.com/services/MYWEBHOOKURLFROMSLACK";
SlackClient client = new SlackClient(WebHookUrl);
client.PostMessage(username: "tester", text: "Testing Slack Integration!", channel: "#random");
}
The error I get is as follows:
The request was aborted: Could not create SSL/TLS secure channel.
So it seems I have an issue with my PostMessage method, with the URI return. From what I've researched, it should just work! My web hook is validated and set up correctly in Slack.
Any help is much appreciated!!

Slack requires TLS 1.2 and above
That said, replace SecurityProtocolType.Tls (TLS 1) with SecurityProtocolType.Tls12(TLS 1.2)
REF: SecurityProtocolType Enum
Hth.

im getting a error 401 unauthorized using the spotify api in c# wpf

Im getting this Error. System.Net.WebException: 'The remote server returned an error: (401) Unauthorized.' Code is provided below.
When i take out the method "PrintUsefulData(api)", everything seems to work fine
that method has a http client webrequest. Im trying to request the following https://api.spotify.com/v1/albums.
static void Main(string[] args)
{
_clientId = string.IsNullOrEmpty(_clientId)
? Environment.GetEnvironmentVariable("my_clientId")//my id
: _clientId;
_secretId = string.IsNullOrEmpty(_secretId)
? Environment.GetEnvironmentVariable("my_secretId") // my id
: _secretId;
AuthorizationCodeAuth auth =
new AuthorizationCodeAuth(_clientId, _secretId, "http://localhost:5002", "http://localhost:5002", Scope.PlaylistReadPrivate | Scope.PlaylistReadCollaborative);
auth.AuthReceived += AuthOnAuthReceived;
auth.Start();
auth.OpenBrowser();
Console.ReadLine();
auth.Stop(0);
}
private static async void AuthOnAuthReceived(object sender,
AuthorizationCode payload)
{
AuthorizationCodeAuth auth = (AuthorizationCodeAuth)sender;
auth.Stop();
Token token = await auth.ExchangeCode(payload.Code);
SpotifyWebAPI api = new SpotifyWebAPI
{
AccessToken = token.AccessToken,
TokenType = token.TokenType
};
PrintUsefulData(api);
}
private static async void PrintUsefulData(SpotifyWebAPI api)
{
RestClient rClient = new RestClient();
rClient.endPoint = "https://api.spotify.com/v1/albums";
string strResponse = string.Empty;
strResponse = rClient.getRequest();
}
}
}
public enum HttpVerb
{
GET,
POST,
PUT,
DELETE
}
class RestClient
{
public string endPoint { get; set; }
public HttpVerb httpMethod { get; set; }
public RestClient()
{
endPoint = string.Empty;
httpMethod = HttpVerb.GET;
}
public string getRequest()
{
string strResponseVal = string.Empty;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(endPoint);
request.Method = httpMethod.ToString();
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
if (response.StatusCode != HttpStatusCode.OK)
{
throw new ApplicationException("error code: " + response.StatusCode);
}
using (Stream responseStream = response.GetResponseStream())
{
if (responseStream != null)
{
using (StreamReader reader = new StreamReader(responseStream))
{
strResponseVal = reader.ReadToEnd();
}
}
}
}
return strResponseVal;
}
}
}

There could be a couple of things going on here but here's my shot at helping based on what code you've posted:
Token Expiration - If you get a 401 error on a request then you need to use the Refresh Token which should have been supplied at the point of authorisation to get a new Access Token. This should apply to ANY call you make to the API.
Request Parameters - The endpoint you're calling (https://api.spotify.com/v1/albums) requires the parameter ids so the Spotify API knows what 'albums' you would like to return.
More info: https://developer.spotify.com/documentation/web-api/reference/albums/get-several-albums/
Another thing to check:
- Scope - make sure when you Auth to the API you are setting the required scope you need to perform actions in the future. I don't think this applies specifically in this case but worth noting.

Object null in WebApi method after PostAsJsonAsync

I am posting an object to a WebApi method. I'm using PostAsJsonAsync to do this.
public async Task<HttpResponseMessage> PostAsync(string token, ServiceCall call)
{
var client = new HttpClient();
client.SetBearerToken(token);
var response = await client.PostAsJsonAsync(Uri + "id/nestedcall", call);
return response;
}
The object call that I'm passing is not null when I post it.
[HttpPost]
[Route("id/nestedcall")]
public async Task<IHttpActionResult> NestedCall([FromBody]ServiceCall call)
{
// call is null here
}
However it is null in my API method. I can't seem to work out why as all of the examples I've followed use this format.
Why isn't the call object being picked up by the web api?
Edit
Here is the ServiceCall object. It is in a separate class library and a reference is included in both the web application and the API.
public class ServiceCall
{
public ServiceCall(Service service, string grantType)
{
ClientId = service.Id;
ClientSecret = service.Secret;
Uri = service.Uri;
Scope = service.Scope;
GrantType = grantType;
}
public ServiceCall(string clientid, string clientsecret, string uri, string scope, string grantType)
{
ClientId = clientid;
ClientSecret = clientsecret;
Uri = uri;
Scope = scope;
GrantType = grantType;
}
public string ClientId { get; set; }
public string ClientSecret { get; set; }
public string Uri { get; set; }
public string Scope { get; set; }
public string GrantType { get; set; }
}

I have seen Object null in WebApi method after PostAsJsonAsync due to serialization.
Better to use PostAsync like below :
var obj = new MyClass()
{
MyProperty = 11
};
using (var client = new HttpClient())
{
string inputJson = Newtonsoft.Json.JsonConvert.SerializeObject(obj);
HttpContent inputContent = new StringContent(inputJson, Encoding.UTF8, "application/json");
HttpResponseMessage response1 = client.PostAsync("http://localhost:60909/api/home/Test", inputContent).Result;
if (response1.IsSuccessStatusCode)
{
}
}

Using Prefix Stackify I was able to diagnose that the serialiser was throwing an exception:
Newtonsoft.Json.JsonSerializationException: Unable to find a constructor to use for type Core.Models.ServiceCall. A class should either have a default constructor, one constructor with arguments or a constructor marked with the JsonConstructor attribute. Path 'ClientId', line 1, position 12.
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateNewObject
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize
However, very helpfully, rather than tell me that an exception occurred the controller simply gave me a null object.
As hinted by the exception the solution is to add a default constructor (or at least one the serialiser can understand).
public ServiceCall()
{
}

looks like the JSON serialization may be failing. BTW, remove that [FromBody] and try without it like below. PostAsJsonAsync method serializes the ServiceCall object to JSON and then sends the JSON payload in a POST request.
public async Task<IHttpActionResult> NestedCall(ServiceCall call)
{
// your code
}

I run into exactly the same problem and had to do this to solve it:
using (var client = new HttpClient())
{
client.SetBearerToken(token);
var content = new StringContent(JsonConvert.SerializeObject(call), Encoding.UTF8, "application/json");
var response = await client.PostAsJsonAsync(Uri + "id/nestedcall", content);
return response;
}