how to send Content-Disposition: form-data; name="name" in correct way when call post api from C# to avoid statuserror 500 - xmlhttprequest

Question

public async Task<T> PostFrom<T>(string baseAddress, string url, string requestbody)
{
T obj = default(T);
//Create the Uri string
string request = baseAddress + url;
WriteLog(request + " : " + "start");
try
{
//Create the Uri
var urirequest = new Uri(request);
//define MultipartFormDataContent
var multipart = new MultipartFormDataContent();
//Add Content-Type
multipart.Headers.Remove("Content-Type");
multipart.Headers.TryAddWithoutValidation("Content-Type", "multipart/form-data; boundary=" + financialAuth.Value.ContentType.boundary);
//Add AuthToken
multipart.Headers.Add("AuthToken", financialAuth.Value.AuthToken);
//start adding the Content-Disposition which i have 3 of them
//1st Content-Disposition form-data; name="SearchCriteria" "requestbody" is the json
if (!string.IsNullOrEmpty(requestbody))
{
var requestbodyContent = new StringContent(JsonConvert.SerializeObject(requestbody));
requestbodyContent.Headers.Add("Content-Disposition", "form-data; name=\"SearchCriteria\"");
multipart.Add(requestbodyContent, "SearchCriteria");
}
//2nd Content-Disposition form-data; name="Secret" "financialAuth.Value.Secret" is the string
var secretContent = new StringContent(financialAuth.Value.Secret);
secretContent.Headers.Add("Content-Disposition", "form-data; name=\"Secret\"");
multipart.Add(secretContent, "Secret");
//3rd Content-Disposition form-data; name="AppID" "financialAuth.Value.AppID" is the string
var appIdContent = new StringContent(financialAuth.Value.AppID);
appIdContent.Headers.Add("Content-Disposition", "form-data; name=\"AppID\"");
multipart.Add(appIdContent, "AppID");
//define the HttpRequestMessage of type post
var httpRequestMessage = new HttpRequestMessage(HttpMethod.Post, urirequest);
//assign the multipart of httpRequestMessage.Content
httpRequestMessage.Content = multipart;
//assign the urirequest of httpClient.BaseAddress
client.BaseAddress = urirequest;
WriteLog("start url" + request);
/* Here when I call the post web api I'm getting below error:
{{StatusCode: 500, ReasonPhrase: 'Internal Server Error', Version: 1.1, Content: System.Net.Http.HttpConnection+HttpConnectionResponseContent,
Headers: {
Cache-Control: no-cache
Pragma: no-cache
Server: Microsoft-IIS/8.5
X-AspNet-Version: 4.0.30319
Access-Control-Allow-Origin: *
Access-Control-Allow-Headers: Content-Type,authtoken
Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS
Date: Tue, 26 Feb 2019 14:59:51 GMT
Content-Type: application/json; charset=utf-8
Expires: -1
Content-Length: 36
}}
*/
HttpResponseMessage response = await client.SendAsync(httpRequestMessage).ConfigureAwait(false);
WriteLog("END url" + request);
if (response.IsSuccessStatusCode)
{
WriteLog(request + " : " + "Begin Result");
string result = await response.Content.ReadAsStringAsync();
obj = JsonConvert.DeserializeObject<T>(result);
WriteLog(request + " : " + "End Result");
}
}
catch (Exception ex)
{
WriteLog(request + " " + ex.Message);
}
return obj;
}

Answer 1

I just solved the error by commenting the below code:
// Add Content-Type
multipart.Headers.Remove("Content-Type");
multipart.Headers.TryAddWithoutValidation("Content-Type", "multipart/form-data; boundary=" + financialAuth.Value.ContentType.boundary);
It seems the content type will be created automatically by MultipartFormDataContent.
Thanks for looking into my issue.