REST C# 401/403 Error. Problem Retrieving share link

Hi,
I am trying to use REST to retrieve a file sharing link but I am receiving either error 401 or 403. The error I receive varies according to the tests that I try to run lol.

I have the following method:

static string HttpPost(string url, string[] paramName, string[] paramVal)
    {
        var req = WebRequest.Create(new Uri(url))
                             as HttpWebRequest;
        req.Method = "POST";
        req.ContentType = "application/x-www-form-urlencoded";
        req.Accept = "*/*";

        // Build a string with all the params, properly encoded.
        // We assume that the arrays paramName and paramVal are
        // of equal length:
        var paramz = new StringBuilder();

        for (int i = 0; i < paramName.Length; i++)
        {
            paramz.Append(paramName[i]);
            paramz.Append("=");
            paramz.Append(HttpUtility.UrlEncode(paramVal[i]));
            paramz.Append("&");
        }

        // Encode the parameters as form data:
        byte[] formData =
            UTF8Encoding.UTF8.GetBytes(paramz.ToString());
        req.ContentLength = formData.Length;

        // Send the request:
        using (var post = req.GetRequestStream())
        {
            post.Write(formData, 0, formData.Length);
        }

        // Pick up the response:
        string result = null;
        using (var resp = req.GetResponse()
                                      as HttpWebResponse)
        {
            var reader =
                new StreamReader(resp.GetResponseStream());
            result = reader.ReadToEnd();
        }

        return result;
    }

I pass as parameter the following:
url: https://api.dropbox.com/1/shares/auto/path
parameters
values

In my first try, I have tried passing as parameters as parameter the following:
oauth_consumer_key, oauth_nonce, oauth_signature_method, oauth_timestamp, oauth_token, oauth_version, oauth_signature

As a result, I have received Error 403 Forbidden. so I assumed I was receiving this error because of authentication which is funny because I am passing through the parameters, so then I did the following:

included those parameters after the url just like the example below:

https://api-content.dropbox.com/1/shares/auto/PATH?oauth_consumer_key=XXX&oauth_nonce=XXX&oauth_signature_method=HMAC-SHA1&oauth_timestamp=1434773930&oauth_token=XXX&oauth_version=1.0&oauth_signature=XXX 

As a result I have received error 401 Unauthorized.

I am obtaining file URI through SharpBox, using the following:
var uri = dropBoxStorage.GetFileSystemObjectUrl(file.Name, folder);
Would anyone know why I am not able to retrieve that sharing link?