A method was called at an unexpected time in HttpClient MultipartFormDataContent

Question

I have to post the multipart data to the server but I am getting below error

I am using the below code

  public async static Task<string> HttpImagePostMethod(byte[] wInputData, string Uri, string path)
    {
        string result = string.Empty;
        try
        {
            #region For Https (Secure) Api having SSL
            var filter = new HttpBaseProtocolFilter();
            filter.IgnorableServerCertificateErrors.Add(Windows.Security.Cryptography.Certificates.ChainValidationResult.Untrusted);
            var client = new System.Net.Http.HttpClient(new WinRtHttpClientHandler(filter));
            #endregion

            MultipartFormDataContent requestContent = new MultipartFormDataContent();

            //   StreamContent content = new StreamContent(wInputData);
            var content = new ByteArrayContent(wInputData);
            content.Headers.ContentType = new MediaTypeHeaderValue("image/jpg");

            requestContent.Add(content, "file", path);               
            requestContent.Headers.Add("X-API-Key", UrlFactory.X_API_Key_Value);
            requestContent.Add(new StringContent("144"), "type");

            HttpResponseMessage aResp = await client.PostAsync(UrlFactory.BaseUrl + Uri, requestContent);

            if (aResp.IsSuccessStatusCode)
            {
                result = await aResp.Content.ReadAsStringAsync();
            }
            else
            {
                result = await aResp.Content.ReadAsStringAsync();
            }
        }
        catch (Exception ex)
        {
            result = string.Empty;
        }
        return result;
    }

I am getting error at this line

HttpResponseMessage aResp = await client.PostAsync(UrlFactory.BaseUrl + Uri, requestContent);

Due to this line

requestContent.Headers.Add("X-API-Key", UrlFactory.X_API_Key_Value);

Answer 1

Myself Answer this question maybe helpful to my other friends...

  HttpRequestMessage httpRequest = new HttpRequestMessage();
            httpRequest.Method = HttpMethod.Post;
            httpRequest.RequestUri = new System.Uri(UrlFactory.BaseUrl + Uri);
            httpRequest.Content = requestContent;

            httpRequest.Headers.TryAddWithoutValidation("Content-Type", "application/x-www-form-urlencoded");
            httpRequest.Headers.TryAddWithoutValidation("X-API-Key", UrlFactory.X_API_Key_Value);

Client(HttpClient) shouldn't contain any header, we declaring header in HttpRequestMessage

Answer 2

As the error message says, you're trying to set a header on the content but it doesn't belong there; your API token is a property of the request itself and not of its content.
Try adding that header to client.DefaultRequestHeaders instead.