如何使用 C# HttpClient 发送未编码的表单数据

Question

I'm trying to "repurpose" a third-party API used by a desktop application. I've found that the below code gets me very close to matching the packets sent by the app:

var formData = new FormUrlEncodedContent(new[]
{
    new KeyValuePair<string, string>(JsonConvert.SerializeObject(myPayload), "")
});

var response = Client.PostAsync(myURL, formData).Result;
var json = response.Content.ReadAsStringAsync().Result;

This gets me almost exactly the same payload sent by the application, except it encodes the data (I know, "encoded" is right there in the name). I need to get the exact same request but without the data being encoded, but I can't quite find the right object(s) to pull it off. How do I keep this payload from being URL encoded?

Edit:

This is a login request I pulled from Wireshark emanating from the application:

POST /Login HTTP/1.1
Content-Type: application/x-www-form-urlencoded
Host: 1.1.1.1
Content-Length: 161
Expect: 100-continue
Connection: Close

{"username":"myuser","auth-id":"0a0a140f81a2ce0c303386e93cec41bf04660c22a881be9a"}

This is what the above will generate:

POST /Login HTTP/1.1
Expect: 100-continue
Connection: Close
Content-Type: application/x-www-form-urlencoded
Content-Length: 221
Host: 1.1.1.1

%7B%22user-name%22%3A%22myuser%22%2C%22auth-id%22%3A%220a0a140f81a2ce0c303386e93cec41bf04660c22a881be9a%22%7D=

I've edited them for brevity so the Content-Length is wrong. I realize it might not be the best way to send this data, but I have no control over how it's consumed.

Answer 1

Since you're actually trying to send JSON, I think you need to wrap the JSON in a StringContent object rather than a FormUrlEncoded object. Form-encoded data and JSON data are two different ways of formatting a payload (another commonly used format would be XML, for example). Using them both together doesn't make any sense.

I think something like this should work:

var content = new StringContent(JsonConvert.SerializeObject(myPayload), Encoding.UTF8, "application/json");
var response = Client.PostAsync(myURL, content).Result;
var json = response.Content.ReadAsStringAsync().Result;

(PS the Content-Type: application/x-www-form-urlencoded header sent by the application appears to be misleading, since the request body clearly contains JSON. Presumably the receiving server is tolerant of this nonsense, or just ignores it because it's always expecting JSON.)