Trouble including a file in multipart/form-data POST using RestSharp

Question

I'm relatively new to web interactions with C# and I'm having some trouble making a POST request to upload a file using an API. The API only accepts the files as part of a multipart/form-data section in the body. At other's suggestions I've been trying to use RestSharp to do this, but I can't seem to get the file itself into the POST. Chunks of code derived from Postman suggested code - where the POST works.

I've tried a few things. This chunk resulted in a POST going through with the correct parameter in the body, but no file was included.

var client = new RestClient(postURL);
var request = new RestRequest(Method.POST);
request.AddHeader("cache-control", "no-cache");
request.AddHeader("Content-Type", "application/x-www-form-urlencoded");
request.AddHeader("content-type", "multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW");
request.AddParameter("multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW", string.Format("------WebKitFormBoundary7MA4YWxkTrZu0gW\r\nContent-Disposition: form-data; name=\"upfile\"; filename=\"{0}\"\r\nContent-Type: application/xml\r\n\r\n\r\n------WebKitFormBoundary7MA4YWxkTrZu0gW\r\nContent-Disposition: form-data; name=\"overwrite\"\r\n\r\ntrue\r\n------WebKitFormBoundary7MA4YWxkTrZu0gW--", xmlPath), ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
string test = response.Content.ToString();

I also tried some variations of AddFile - physical file path, byte array, and byte array with content type = application/xml. With these iterations, I was able to get a file to post, but the overwrite parameter wasn't coming through correctly to force a file overwrite.

var client = new RestClient(postURL);
var request = new RestRequest(Method.POST);
request.AddHeader("cache-control", "no-cache");
request.AddHeader("Content-Type", "application/x-www-form-urlencoded");
request.AddHeader("content-type", "multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW");
// The different part below
request.AddFile("upfile", @xmlPath);
request.AddParameter("multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW", "------WebKitFormBoundary7MA4YWxkTrZu0gW\r\nContent-Disposition: form-data; name=\"overwrite\"\r\n\r\ntrue\r\n------WebKitFormBoundary7MA4YWxkTrZu0gW--", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
string test = response.Content.ToString();

*note: I'm using an older version of RestSharp (105.2.3) to be compatible with .Net 4.0 (stuck with it in this case).

Any ideas as to what I'm doing wrong here?

Answer 1

Figured it out after sleeping on it, was really simple in the end. All of the extra webkit and multipart stuff that was throwing me for a loop is entirely unnecessary - autogenerated code from Postman is overly complicated it seems.

var client = new RestClient(postURL);
var request = new RestRequest(Method.POST);
request.AddHeader("cache-control", "no-cache");
request.AddHeader("Content-Type", "application/x-www-form-urlencoded");
request.AddHeader("content-type", "multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW");
request.AddFile("upfile", @xmlPath);
request.AddParameter("overwrite", "true", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
string test = response.Content.ToString();