The remote server returned an error (400) bad request when i request linkedin using social oauth

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WebAPI

OAuth

Hi,
I am getting an error when i request to linke in access token url uing socail Oauth 2.0


The line request.GetResponse() getting this error.

What I have tried:

public static string Request(string url, string method, string contentType, NameValueCollection header,
            string data, string proxyAddress = null)
        {
            var request = (HttpWebRequest) WebRequest.Create(url);
            request.Method = method;
            if (!string.IsNullOrEmpty(contentType))
                request.ContentType = contentType;
            if (header != null)
                request.Headers.Add(header);

            if (!string.IsNullOrEmpty(proxyAddress))
            {
                IWebProxy proxy = new WebProxy(proxyAddress);
                proxy.Credentials = new NetworkCredential();
                request.Proxy = proxy;
            }

            if (!string.IsNullOrEmpty(data))
            {
                using (var swt = new StreamWriter(request.GetRequestStream()))
                {
                    swt.Write(data);
                }
            }

            string result = string.Empty;
            using (WebResponse response = request.GetResponse())
            {
                using (var sr = new StreamReader(response.GetResponseStream()))
                {
                    result = sr.ReadToEnd();
                }
            }
            return result;
        }