Send form-data using HttpClient C#

Question

I'm trying to make an API call to third party URL, which is working fine through postman, but same request through C# HttpClient not working.

This is how I'm sending request in postman

C# Sample Code

 var nvc = new List<KeyValuePair<string, string>>();
 nvc.Add(new KeyValuePair<string, string>("PARAM1", "PARAM1 Value"));
 nvc.Add(new KeyValuePair<string, string>("PARAM2", "PARAM2 Value"));
 nvc.Add(new KeyValuePair<string, string>("PARAM3", "PARAM3 Value"));
  var req = new HttpRequestMessage(HttpMethod.Post, "Https://ThirdPartyURL") { 
                Content = new FormUrlEncodedContent(nvc) 
            };

Am I doing anything wrong here?

UPDATE #1: **

Fiddler Traces for postman request(which is working fine)

Fiddler Traces for C# Request(which is failing)

Thanks in advance!

Regards, Moksh

I see you're using `FormUrlEncodedContent` and in Postman is selected `form-data`. `FormUrlEncodedContent` sends `Content-Type: application/x-www-form-urlencoded; ` and form-data I believe should be `Content-Type: multipart/form-data; boundary=` — dcg, Dec 04 '20 at 18:47
@dcg looks like that's the real issue, I just verified fiddler traces for both postman and C# and found same thing, Do you have sample code like how can we set content-type here ? — Mox Shah, Dec 04 '20 at 18:50
I was just taking a look at [this](https://stackoverflow.com/a/3275002/4152153) answer, I think it may help you. — dcg, Dec 04 '20 at 18:51
Also, take a look at [this](https://stackoverflow.com/a/53190314/4152153). There's `MultipartFormDataContent` class. — dcg, Dec 04 '20 at 18:56
@dcg well, Earlier I tried `MultipartFormDataContent` but that was throwing 400 bad request. — Mox Shah, Dec 04 '20 at 18:59
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/225542/discussion-between-mox-shah-and-dcg). — Mox Shah, Dec 04 '20 at 19:16

score 0 · Answer 1 · answered Dec 04 '20 at 22:52

Instead of

var nvc = new List<KeyValuePair<string, string>>();

try to create a new class:

public class RecipientSender
{
public string Recipient_First_Name {get; set;}
public string Recipient_Last_Name {get; set;}
.....
}

and create httpclientrequest like this:

....
....

var recipientSender=new RecipientSender { Recipient_FirstName=..., }
var contentType = new MediaTypeWithQualityHeaderValue("application/json");
httpClient.DefaultRequestHeaders.Accept.Add(contentType);
var stringData = JsonConvert.SerializeObject(recipientSender);
contentData = new StringContent(stringData, Encoding.UTF8, "application/json");
var httpResponseMessage=client.PostAsync(url, contentData);
.....

Send form-data using HttpClient C#

1 Answers1